0300-9629/92$5.00+ 0.00 0 1991Pergamon Press plc
Con~p.Biochem.Physiol.Vol. IOIA,No. I, pp. 161-166,1992 Printed in Great Britain
EFFECT OF EARLY POSTNATAL LONG-TERM FASTING ON THE DEVELOPMENT OF PEPTIDE HYDROLYSIS IN CHICKS I. TARVID Institute of Biology, Latvian Academy of Sciences, Miera Street 3, Salaspils, Latvia, 229021, U.S.S.R. Telephone: 947306 fReeeked 25 March 1991) Abstract-l. Early development of peptide hydrolysis in the digestive tract was investigated in experiments with fasted and fed ad lib. chicks during the first decade of postnatal period. 2. Pancreatic carboxypeptidase A (CPA) activity was maximal at the moment of hatch. On the second day CPA activity considerably diminished in starved and fed animal groups; further starvation (3-4 days) led to the significant increase of CPA total and specific activity, whereas the amount of enzyme in pancreas of fed chicks was rather low. 3. Aminopeptidase (AP) activity of the small intestinal surface was less sensitive to starvation. The increase of activity in all intestinal parts was observed only on the 4th day of fasting. The most sensitive to starvation were dipeptidases. Changes in their activity (2-fold increase) were detected after 24 hr of starvation. 4. The formation of specific physiological proximo-distal gradient of intestinal exopeptidase activities
began only after the moment of the first feeding. 5. This gives evidence that the development of peptide hydrolysis depends not only on the age of the animal but also on the normal physiological beginning of the process of exogenous nutrition.
Experiments carried out on birds detected a sharp fall in the hydrolysis rate of peptide substrates down to lo-25% of the initial levels during the first week (Tarvid and Kushak, 1983a; Tarvid, 1991). Taking into consideration that the most intensive decrease of the exopeptidase activity takes place in the first 5 days it was of interest to trace the time course of this process day by day, to determine the effect of the beginning of food intake as well as prolonged fasting on the development of peptide hydrolysis function during the early postnatal period. The article represents the results of a combined and simultaneous study of the activity of three classes of exopeptidases: pancreatic carboxypeptidase A and intestinal aminopeptidases and dipeptidases (McDonald and Barrett, 1985) during the first 10 days in the control chicks (under normal feeding regime) and in the experimental group where the first feeding was allowed on the fifth day after hatching.
INTRODUCTION
Th’z development and adaptation of the protein digestion in prenatal and postnatal periods have been intensively investigated in the animals of different spscies (Lindberg and Karlsson, 1970; Lindberg er ,rZ., 1975; Corring, 1980; Ruckebusch et al., 1983; ALstic, 1985). These studies were mainly done on pa lcreatic proteases and intestinal dipeptidases. Multiple experimental data, notwithstanding their heterogeneous and in some aspects, contradictory ch;!racter, on the whole show that during the course of Ihe embryonic development of diflerent mammalian species the activity of pancreatic endopeptidases increases in parallel to the maturing of the gastrointestinal tract and reaches its maximum just before bir:h t~~nthal er al., 1981; Austic, 1985). The reported data on further development of protein digestive systems are contradictory. It has been shelwn that in rats the activity of pancreatic proteases dec reased immediately after birth (Austic, 1985). Other investigators have found that in pigs (Hartman et al., 19rll) and rats (Robberecht, 1971) the activity of pa:lcreatic proteases: trypsin and chymotrypsin increases continuously after birth. In the case of rats the grc,wth of the activity was detected only starting from the end of the second week. Similar results were shtnwn for intestinal hydrolases. The activity of dipeptidases in mammals of various species increased, independently of the substrates used, during the period of embryonic development and reached its maximum just before the birth (Lindberg er al., 1975). At the beginning of the postnatal period there was a significant fall in the intensity of hydrolysis of peptide substrates down to the levels characteristic for adult and mature animals. CBP,\ IO,~,--K
MATERIALS AND METHODS Animals High Sex White cross chicks (G&us domesticus) were used starting from hatching and up to tenth day. Special experiments devoted to the investigation of aminopeptidase activity distribution along the surface of the small intestine were carried out in chicks up to the age of 45 days. The following groups of chicks were organized: the initial levels of enzyme activity in one-day-old chicks were assayed on birds 10-15 hr after hatching; chicks of this group had no access to food and water; the control group had free access to water and food. Birds were fed a commercial starting diet for chicks, containing al1 the necessary components. An experimental group had free access to water but was not fed for 4 days after hatching. Enzyme activity was assayed on 161
162
I. TARVID
each successive day for chicks from both the control and experimental groups. A special group of birds was fed only on the fifth day. They were used in experiments on the fifth
and tenth days.
Table 1. Activity of pancreatic carboxypeptidase A in fasted and fed chicks during the first 5 days of postnatal period Activity Chick age (days)
Enzyme preparations After decapitation the abdominal cavity of the chicks was opened and the pancreas and small intestine, excluding the
I 2 3 4 5*
dhodenum, were removed. Small intestine was washed by 5-10 ml of cold (4°C) Rineer solution (DH 7.4) and divided into three equal‘ parts: proximal, medial and’ distal. Each part was used to prepare an everted intestinal segment of
I 2 3 4 5*
I 2 3 4 5*
Enzyme assays
Statistical analysis Experimental data were statistically treated to determine Student’s criterion using standard programs on an IBM PC AT. All results given in the tables are means + SD.
RESULTS
CPA The results given in Table 1 show that in chicks, which did not receive food, the maximal fall in the pancreatic CPA activity took place during the first day. Later the total CPA activity increased up to the initial level and even surpassed it. The decrease of activity for fed chicks was more expressed and reached 86%. The CPA activity level in fed chicks was considerably lower than in fasted ones (approximately 3-10 times) through the whole investigation period. Feeding, started after a day’s fasting, was followed by a sharp fall in the total pool of CPA activity in the pancreas; the activity level decreased from 4.99 + 0.74 to 0.18 f 0.05 mkmol of released leucine. The CPA activity expressed on 1 g of wet tissue showed a similar pattern observed for the total activity. The single difference was the fact that on the fourth day the CPA activity in fasted chicks reached
A
Fed chicks (N = 5)
2.86 0.86 4.11 4.99
mkmol of released Boc-gly-leu f 0.37 f 0.19 P < 0.01 0.37 f 0.04 f0.64 P
Con~p.Biochem.Physiol.Vol. IOIA,No. I, pp. 161-166,1992 Printed in Great Britain
EFFECT OF EARLY POSTNATAL LONG-TERM FASTING ON THE DEVELOPMENT OF PEPTIDE HYDROLYSIS IN CHICKS I. TARVID Institute of Biology, Latvian Academy of Sciences, Miera Street 3, Salaspils, Latvia, 229021, U.S.S.R. Telephone: 947306 fReeeked 25 March 1991) Abstract-l. Early development of peptide hydrolysis in the digestive tract was investigated in experiments with fasted and fed ad lib. chicks during the first decade of postnatal period. 2. Pancreatic carboxypeptidase A (CPA) activity was maximal at the moment of hatch. On the second day CPA activity considerably diminished in starved and fed animal groups; further starvation (3-4 days) led to the significant increase of CPA total and specific activity, whereas the amount of enzyme in pancreas of fed chicks was rather low. 3. Aminopeptidase (AP) activity of the small intestinal surface was less sensitive to starvation. The increase of activity in all intestinal parts was observed only on the 4th day of fasting. The most sensitive to starvation were dipeptidases. Changes in their activity (2-fold increase) were detected after 24 hr of starvation. 4. The formation of specific physiological proximo-distal gradient of intestinal exopeptidase activities
began only after the moment of the first feeding. 5. This gives evidence that the development of peptide hydrolysis depends not only on the age of the animal but also on the normal physiological beginning of the process of exogenous nutrition.
Experiments carried out on birds detected a sharp fall in the hydrolysis rate of peptide substrates down to lo-25% of the initial levels during the first week (Tarvid and Kushak, 1983a; Tarvid, 1991). Taking into consideration that the most intensive decrease of the exopeptidase activity takes place in the first 5 days it was of interest to trace the time course of this process day by day, to determine the effect of the beginning of food intake as well as prolonged fasting on the development of peptide hydrolysis function during the early postnatal period. The article represents the results of a combined and simultaneous study of the activity of three classes of exopeptidases: pancreatic carboxypeptidase A and intestinal aminopeptidases and dipeptidases (McDonald and Barrett, 1985) during the first 10 days in the control chicks (under normal feeding regime) and in the experimental group where the first feeding was allowed on the fifth day after hatching.
INTRODUCTION
Th’z development and adaptation of the protein digestion in prenatal and postnatal periods have been intensively investigated in the animals of different spscies (Lindberg and Karlsson, 1970; Lindberg er ,rZ., 1975; Corring, 1980; Ruckebusch et al., 1983; ALstic, 1985). These studies were mainly done on pa lcreatic proteases and intestinal dipeptidases. Multiple experimental data, notwithstanding their heterogeneous and in some aspects, contradictory ch;!racter, on the whole show that during the course of Ihe embryonic development of diflerent mammalian species the activity of pancreatic endopeptidases increases in parallel to the maturing of the gastrointestinal tract and reaches its maximum just before bir:h t~~nthal er al., 1981; Austic, 1985). The reported data on further development of protein digestive systems are contradictory. It has been shelwn that in rats the activity of pancreatic proteases dec reased immediately after birth (Austic, 1985). Other investigators have found that in pigs (Hartman et al., 19rll) and rats (Robberecht, 1971) the activity of pa:lcreatic proteases: trypsin and chymotrypsin increases continuously after birth. In the case of rats the grc,wth of the activity was detected only starting from the end of the second week. Similar results were shtnwn for intestinal hydrolases. The activity of dipeptidases in mammals of various species increased, independently of the substrates used, during the period of embryonic development and reached its maximum just before the birth (Lindberg er al., 1975). At the beginning of the postnatal period there was a significant fall in the intensity of hydrolysis of peptide substrates down to the levels characteristic for adult and mature animals. CBP,\ IO,~,--K
MATERIALS AND METHODS Animals High Sex White cross chicks (G&us domesticus) were used starting from hatching and up to tenth day. Special experiments devoted to the investigation of aminopeptidase activity distribution along the surface of the small intestine were carried out in chicks up to the age of 45 days. The following groups of chicks were organized: the initial levels of enzyme activity in one-day-old chicks were assayed on birds 10-15 hr after hatching; chicks of this group had no access to food and water; the control group had free access to water and food. Birds were fed a commercial starting diet for chicks, containing al1 the necessary components. An experimental group had free access to water but was not fed for 4 days after hatching. Enzyme activity was assayed on 161
162
I. TARVID
each successive day for chicks from both the control and experimental groups. A special group of birds was fed only on the fifth day. They were used in experiments on the fifth
and tenth days.
Table 1. Activity of pancreatic carboxypeptidase A in fasted and fed chicks during the first 5 days of postnatal period Activity Chick age (days)
Enzyme preparations After decapitation the abdominal cavity of the chicks was opened and the pancreas and small intestine, excluding the
I 2 3 4 5*
dhodenum, were removed. Small intestine was washed by 5-10 ml of cold (4°C) Rineer solution (DH 7.4) and divided into three equal‘ parts: proximal, medial and’ distal. Each part was used to prepare an everted intestinal segment of
I 2 3 4 5*
I 2 3 4 5*
Enzyme assays
Statistical analysis Experimental data were statistically treated to determine Student’s criterion using standard programs on an IBM PC AT. All results given in the tables are means + SD.
RESULTS
CPA The results given in Table 1 show that in chicks, which did not receive food, the maximal fall in the pancreatic CPA activity took place during the first day. Later the total CPA activity increased up to the initial level and even surpassed it. The decrease of activity for fed chicks was more expressed and reached 86%. The CPA activity level in fed chicks was considerably lower than in fasted ones (approximately 3-10 times) through the whole investigation period. Feeding, started after a day’s fasting, was followed by a sharp fall in the total pool of CPA activity in the pancreas; the activity level decreased from 4.99 + 0.74 to 0.18 f 0.05 mkmol of released leucine. The CPA activity expressed on 1 g of wet tissue showed a similar pattern observed for the total activity. The single difference was the fact that on the fourth day the CPA activity in fasted chicks reached
A
Fed chicks (N = 5)
2.86 0.86 4.11 4.99
mkmol of released Boc-gly-leu f 0.37 f 0.19 P < 0.01 0.37 f 0.04 f0.64 P
