Antidiuretic hormone stimulation of adenylate cyclase in semicircular canal epithelium.
Basal adenosine 3',5'-cyclic monophosphate (cAMP) content and the modulation of its production were studied in the frog's semicircular canal epithelium. This epithelium secretes endolymph, a K(+)-rich, positively polarized fluid. The basal cAMP content measured by microradioimmunoassay was 244 +/- 14.2 fmol/structure per 5 min (n = 30). This content was increased about 8 times by 10(-5) M forskolin. Vasotocin, the frog antidiuretic hormone, increased the cAMP production by factors of 1.3 and 3.3 at concentrations of 10(-8) M and 10(-7) M, respectively. This stimulatory effect of vasotocin was blunted by the addition of alpha 2-adrenergic agonists, such as 10(-8) M-10(-5) M norepinephrine, in the presence of 10(-5) M propranolol, or 10(-5) M clonidine. Prostaglandin E2 at a concentration of 10(-8) M, which did not affect the cAMP production, did not modify the response to vasotocin. Glucagon (10(-6) M), calcitonin (10(-6) M), and parathyroid hormone (10 units/ml) did not affect the cAMP content. Prostaglandin E2 (10(-7) M) and the beta-adrenergic agonist isoproterenol (10(-6) M) stimulated the cAMP production by a factor of 1.6. These results indicate that the frog semicircular canal is a target of both vasotocin and catecholamines and that catecholamines through alpha 2-receptors modulate vasotocin-induced cAMP generation. Further, this interaction might be of physiological relevance in the modulation of ion transport in this structure.
INSERM U.251, Département de Physiologie, Faculté Xavier Bichat, Université Paris, France.
E
E
Ferrary
C
C
Bernard
G
G
Friedlander
O
O
Sterkers
C
C
Amiel
D000262:Adenylyl Cyclases / Q000032:analysis*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002116:Calcitonin / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004710:Endolymph / Q000201:enzymology; D004848:Epithelium / Q000201:enzymology / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D009924:Organ Culture Techniques; D010281:Parathyroid Hormone / Q000494:pharmacology; D011893:Rana esculenta; D012665:Semicircular Canals / Q000201:enzymology* / Q000378:metabolism; D014667:Vasopressins / Q000494:pharmacology*; D014668:Vasotocin / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D010281:Parathyroid Hormone; D014667:Vasopressins; D005576:Colforsin; D002116:Calcitonin; D005934:Glucagon; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D015232:Dinoprostone; D007545:Isoproterenol; D003000:Clonidine; D014668:Vasotocin; D009638:Norepinephrine