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.
Ferrary
E
E
INSERM U.251, Département de Physiologie, Faculté Xavier Bichat, Université Paris, France.
Bernard
C
C
Friedlander
G
G
Sterkers
O
O
Amiel
C
C
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