Morphologic Abnormalities in Potassium-Deficient Dogs C. L. Tate, VMD, W. J. Bagdon, PhD, and D. L. Bokelman, DVM, PhD
Potassium deficiency was produced in 16 dogs by means of a diet containing less than 0.03% potassium. Decreases in serum potassium were first observed after 3 weeks. Morphologic changes occurred only in heart, skeletal muscle, and kidney. Focal myocardial necrosis was observed in 6 of 16 deficient dogs, and skeletal muscle degeneration and necrosis were observed in 14 of 16 deficient dogs. A complex nephropathy consisting primarily of epithelial hypertrophy and hyperplasia in the collecting tubules of the inner stripe of the outer medulla occurred in all the deficient dogs. (Am J Pathol 93:103-116, 1978)
M ORPHOLOGIC CHANGES due to potassium deficiency have been studied in many species, including humans,"q monkevs,5 rabbits,6'7 hamsters,8 mice,9 rats,1>2' dogs,231 cats,21 pigs,12 cattle,32 and chicks.33 The causes of potassium deficiency are many; in humans, diarrheal diseases, hyperadrenalism, and renal lesions are common causes." Experimentally, potassium-deficient diets,8'29 corticosteroids,22 25 and hemodialvsis 3" have been used to produce potassium deficiency in animals. NMany organs have been reported to be affected by potassium deficiencv, and there is considerable variation between species. To this variation between species can be added the confusion of conflicting experimental results. For example, Darrow and Nliller22 reported renal lesions associated with potassium deficiency in dogs; since then, absence of renal lesions in potassium-deficient dogs was reported by one author,23 calcification bv another,24 and vacuolation of the proximal tubular epithelium by a third.2` These authors and others 29 have all reported the absence of cardiac lesions. The purpose of this study was to elucidate the morphologic changes produced by a diet deficient in potassium and particularlv to ascertain if renal lesions develop under this regimen. Materials and Methods Two separate but similar studies were performed insolsing a total of 32 beagle dogs. aged 6 to 11 months. The first was a pilot study in which tswo groups of 2 males and 2 females each were fed two different potassium-deficient rations (Hartroff formulation, General Biochemicals, Inc., Chagrin Falls, Ohio, and low potassium" diet, Nutritional From the Department of Safets Assessment. \Merck Institute for Therapeutic Research. West Point. Pennsvlvania. Accepted for publication May 29. 1978, Address reprint requests to Dr Charles L. Tate. Department of Safetv Assessment. Merck Institute for Therapeutic Research W'est Point. PA 19486. 0002-9440/78/1010-0103$01.00 103
104
TATE ET AL
American Journal of Pathology
Biochemicals, Cleveland, Ohio) to determine w-hich seemed most palatable. After a fesw days, all the dogs were shifted to a pelleted form of the General Biochemicals diet which contained less than 0.03% potassium (Table 1). These dogs were given this diet and deionized water ad libitum. Limited hematologic and serum biochemical studies w-ere performed on these animals. The second studv involved four groups of dogs. Group I contained 4 males and 4 females which were offered 400 grams per day of the pelleted potassium-deficient diet (Hartroff formulation). Group II contained 4 males and 4 females which were pair-fed a potassiumsupplemented diet according to the previous day's food consumption of their partner in Group I. The supplemented diet differed from the deficient diet only in that it contained 2% potassium chloride (Table 1). Group III contained 2 males and 2 females which were allowed the supplemented diet ad libitum. Group IV contained 2 ma'les and 2 females which were given a commercial dog food (Wayne Dog Food, Allied Mills, Inc., Chicago. Ill.) ad libitum. All dogs were given deionized water ad libitum. Food consumption was measured daily. Water intake and urine output swere measured 4 days per week. Electrocardiographic recordings and ophthalmologic examinations were also done several times during the study. Hematologic and serum biochemical studies w-ere performed at ,3-week inters als during the studv. Hematologic studies consisted of the determination of hemoglobin concentration, hematocrit, erythrocvte sedimentation rate, total and differential leukocvte counts. Lee-White clotting time, prothrombin time, and an estimation of numbers of platelets. Serum biochemical tests included quantitative tests for total protein, albumin, glucose. urea nitrogen, creatinine, alkaline phosphatase activity, glutamic oxalacetic transaminase activitv (SGOT), carbon dioxide (CO2), and electrolN-tes (sodium, potassium, chloride. calcium, magnesium, phosphorus, and bicarbonate). Sulfobromophthalein excretion and blood pH were also measured. Urinalvsis consisted of qualitative tests for the detection of protein. glucose. bilirubin. and occult blood. Urine pH and specific gravity were measured and the urine sediment was examined microscopically. Necropsies were performed on all animals of both studies. In instances in w-hich a dog from Group I (second study) died or was killed, the pair-fed partner in Group II \vas killed as soon as practicable thereafter. In the 14th week of each study, the surviving animals were anesthetized with an intravenous dose of a barbiturate and w-ere killed by exsanguination. Weights of brain, heart, liver, kidneys. adrenals, and testes w-ere recorded for these animals, and samples of tissues were fixed in 10%' neutral buffered formalin or Zenker's solution. Samples of six muscles (musculus biceps brachii, m. triceps brachii, m. rectus femoris, m. semitendinosis, m. splenius, and m. longus capitis) were taken from each dog. Microscopic examination of tissue from dogs in Groups I and III included hematoxvlin and eosin (H&E-stained sections of paraffin-embedded samples of brain, spinal cord, sciatic nerve, eve, pituitary, adrenal, thvroid (frequentlv including parathyToid), heart (six standard sections per animal), lung, liser, gallbladder, both kidneys, urinary bladder, thymus, spleen, mesenteric lymph node, stomach, intestine, skeletal muscles, skin, reproductive organs (uterus and ovarv or testis and prostate), and rib. In addition, sections of kidneys were stained by oil red 0, Mallory's periodic acid-shiff (PAS), Table 1-Electrolyte Content of the Semisynthetic Diets
Diet
Na*
Potassium-deficient diet
0.46 0.46
Supplemented diet * Expressed as
percent of wet
diet
K
...
;e
....
..
a.
S.* r
b- .b -e
!
_. it- _.?B
_0
.,
*
,*
Potassium deficiency was produced in 16 dogs by means of a diet containing less than 0.03% potassium. Decreases in serum potassium were first observed after 3 weeks. Morphologic changes occurred only in heart, skeletal muscle, and kidney. Focal myocardial necrosis was observed in 6 of 16 deficient dogs, and skeletal muscle degeneration and necrosis were observed in 14 of 16 deficient dogs. A complex nephropathy consisting primarily of epithelial hypertrophy and hyperplasia in the collecting tubules of the inner stripe of the outer medulla occurred in all the deficient dogs. (Am J Pathol 93:103-116, 1978)
M ORPHOLOGIC CHANGES due to potassium deficiency have been studied in many species, including humans,"q monkevs,5 rabbits,6'7 hamsters,8 mice,9 rats,1>2' dogs,231 cats,21 pigs,12 cattle,32 and chicks.33 The causes of potassium deficiency are many; in humans, diarrheal diseases, hyperadrenalism, and renal lesions are common causes." Experimentally, potassium-deficient diets,8'29 corticosteroids,22 25 and hemodialvsis 3" have been used to produce potassium deficiency in animals. NMany organs have been reported to be affected by potassium deficiencv, and there is considerable variation between species. To this variation between species can be added the confusion of conflicting experimental results. For example, Darrow and Nliller22 reported renal lesions associated with potassium deficiency in dogs; since then, absence of renal lesions in potassium-deficient dogs was reported by one author,23 calcification bv another,24 and vacuolation of the proximal tubular epithelium by a third.2` These authors and others 29 have all reported the absence of cardiac lesions. The purpose of this study was to elucidate the morphologic changes produced by a diet deficient in potassium and particularlv to ascertain if renal lesions develop under this regimen. Materials and Methods Two separate but similar studies were performed insolsing a total of 32 beagle dogs. aged 6 to 11 months. The first was a pilot study in which tswo groups of 2 males and 2 females each were fed two different potassium-deficient rations (Hartroff formulation, General Biochemicals, Inc., Chagrin Falls, Ohio, and low potassium" diet, Nutritional From the Department of Safets Assessment. \Merck Institute for Therapeutic Research. West Point. Pennsvlvania. Accepted for publication May 29. 1978, Address reprint requests to Dr Charles L. Tate. Department of Safetv Assessment. Merck Institute for Therapeutic Research W'est Point. PA 19486. 0002-9440/78/1010-0103$01.00 103
104
TATE ET AL
American Journal of Pathology
Biochemicals, Cleveland, Ohio) to determine w-hich seemed most palatable. After a fesw days, all the dogs were shifted to a pelleted form of the General Biochemicals diet which contained less than 0.03% potassium (Table 1). These dogs were given this diet and deionized water ad libitum. Limited hematologic and serum biochemical studies w-ere performed on these animals. The second studv involved four groups of dogs. Group I contained 4 males and 4 females which were offered 400 grams per day of the pelleted potassium-deficient diet (Hartroff formulation). Group II contained 4 males and 4 females which were pair-fed a potassiumsupplemented diet according to the previous day's food consumption of their partner in Group I. The supplemented diet differed from the deficient diet only in that it contained 2% potassium chloride (Table 1). Group III contained 2 males and 2 females which were allowed the supplemented diet ad libitum. Group IV contained 2 ma'les and 2 females which were given a commercial dog food (Wayne Dog Food, Allied Mills, Inc., Chicago. Ill.) ad libitum. All dogs were given deionized water ad libitum. Food consumption was measured daily. Water intake and urine output swere measured 4 days per week. Electrocardiographic recordings and ophthalmologic examinations were also done several times during the study. Hematologic and serum biochemical studies w-ere performed at ,3-week inters als during the studv. Hematologic studies consisted of the determination of hemoglobin concentration, hematocrit, erythrocvte sedimentation rate, total and differential leukocvte counts. Lee-White clotting time, prothrombin time, and an estimation of numbers of platelets. Serum biochemical tests included quantitative tests for total protein, albumin, glucose. urea nitrogen, creatinine, alkaline phosphatase activity, glutamic oxalacetic transaminase activitv (SGOT), carbon dioxide (CO2), and electrolN-tes (sodium, potassium, chloride. calcium, magnesium, phosphorus, and bicarbonate). Sulfobromophthalein excretion and blood pH were also measured. Urinalvsis consisted of qualitative tests for the detection of protein. glucose. bilirubin. and occult blood. Urine pH and specific gravity were measured and the urine sediment was examined microscopically. Necropsies were performed on all animals of both studies. In instances in w-hich a dog from Group I (second study) died or was killed, the pair-fed partner in Group II \vas killed as soon as practicable thereafter. In the 14th week of each study, the surviving animals were anesthetized with an intravenous dose of a barbiturate and w-ere killed by exsanguination. Weights of brain, heart, liver, kidneys. adrenals, and testes w-ere recorded for these animals, and samples of tissues were fixed in 10%' neutral buffered formalin or Zenker's solution. Samples of six muscles (musculus biceps brachii, m. triceps brachii, m. rectus femoris, m. semitendinosis, m. splenius, and m. longus capitis) were taken from each dog. Microscopic examination of tissue from dogs in Groups I and III included hematoxvlin and eosin (H&E-stained sections of paraffin-embedded samples of brain, spinal cord, sciatic nerve, eve, pituitary, adrenal, thvroid (frequentlv including parathyToid), heart (six standard sections per animal), lung, liser, gallbladder, both kidneys, urinary bladder, thymus, spleen, mesenteric lymph node, stomach, intestine, skeletal muscles, skin, reproductive organs (uterus and ovarv or testis and prostate), and rib. In addition, sections of kidneys were stained by oil red 0, Mallory's periodic acid-shiff (PAS), Table 1-Electrolyte Content of the Semisynthetic Diets
Diet
Na*
Potassium-deficient diet
0.46 0.46
Supplemented diet * Expressed as
percent of wet
diet
K
...
;e
....
..
a.
S.* r
b- .b -e
!
_. it- _.?B
_0
.,
*
,*
