Endocrinol.Japon.

1978,25(5),

Effects the

423-430

of Ethacrynic Acid and Furosemide Hormone-Mediated Adenylate Cyclase Activation of the Hamster Kidney FUMIAKI MARUMO

on

AND TAKAO MISHINA

Department of Medicine, of Medicine, Sagamihara,

Kitasato University, School Kanagawa-ken 228, Japan

Synopsis The effects of ethacrynic acid and furosemide on the adenylate cyclase activity of the hamster kidney and heart were examined. Ethacrynic acid and furosemide suppressed the vasopressin-mediated increment of adenylate cyclase activity much stronger than the basal activity of the renal medulla. Ethacrynic acid and furosemide strongly suppressed the parathyroid hormone-mediated increment of adenylate cyclase activity on the renal cortex, though furosemide could not inhibit the basal activity of the enzyme. Ethacrynic acid and furosemide suppressed the 1-adrenaline-mediated increment of adenylate cyclase activity of the cardiac muscle, while furosemide could not inhibit the basal activity. Ethacrynic acid and furosemide suppressed the NaF-mediated increment of adenylate cyclase activity of the renal medulla. Thus, these diuretics seem to inhibit the catalytic unit of the enzyme. Ethacrynic acid and furosemide strongly suppressed the hormone-mediated increment of the adenylate cyclase activity, while Ca** could only depress it to the same degree as it did the basal activity. This difference suggests that these diuretics inhibit not only the catalytic unit of the enzyme, but also other steps of the adenylate cyclase system. Ethacrynic acid and furosemide suppressed the effect of 5'-guanylylimido-diphosphate [Gpp(NH)p] on the adenylate cyclase activation and strongly inhibited the enzyme activity by using the combination of vasopressin and Gpp(NH)p. These results might suggest that ethacrynic acid and furosemide not only affect the catalytic unit of the adenylate cyclase, but also the GTP sensitive site of the enzyme system.

The adenylate cyclase system is a key control point in the action of biogenic amines, prostaglandins, and peptide hormones, such as vasopressin and parathyroid hormone. However, the adenylate cyclase system is sensitive not only to hormones, but also to other agents such as diuretics. Ethacrynic acid was reported to block the hydroosmotic effect of vasopressin, but not of exogenous cyclic AMP in the toad bladder membrane (Bentley, 1969) or in the microperfused collecting ducts of rabbits (Abramow, 1974). Recently, several obReceived

October

25, 1977.

servations indicating that ethacrynic acid inhibited the renal adenylate cyclase activity were reported (Barnes et al., 1975; Ebel, 1974). In the early stage of the present study, we found ethacrynic acid and furosemide could strongly inhibit the vasopressinmediated increment of adenylate cyclase activity of the renal medulla of hamster, while they only slightly inhibited the basal activity of the enzyme. Therefore, this study was planned to explain the reason why the diuretics gave different actions between the basal activity and vasopressin activation of the adenylate cyclase.

424

MARUMO

AND

Tris. assay.

Methods Female were

golden

used.

rated

after into

in

each

gently

50

mM

in

genizer

in

the

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were

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7.4)

binding

assay

was of

(1970). was

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buffer

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bovine

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ATP-2Na.

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gation

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kinase 200ƒÊl

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Lowry

et

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a crude

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parathyroid

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furosemide

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Effects of ethacrynic acid and furosemide on the hormone-mediated adenylate cyclase activation of the hamster kidney.

Endocrinol.Japon. 1978,25(5), Effects the 423-430 of Ethacrynic Acid and Furosemide Hormone-Mediated Adenylate Cyclase Activation of the Hamster K...
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