Hormonal regulation of adenylate cyclase in the stria vascularis of the mouse.

The adenylate cyclase complex is a ubiquitous 'second-messenger' system mediating the actions of hormones and neurotransmitters. Its presence but not its physiological control and function had previously been established in the cochlea. In this study, the hormonal stimulation of adenylate cyclase activity of the stria vascularis of the CBA mouse was characterized. In the presence of the regulatory nucleotide, GTP, the enzyme was stimulated by isoproterenol and epinephrine with a half-maximal effect at about 10 microM and the stimulation was blocked by propranolol. This profile is consistent with the presence of adrenergic beta 2-receptors on the strial enzyme complex. Hormones and neuromodulators preferring other receptor subtypes were ineffective; the non-specific stimulator, forskolin, activated the enzyme. The finding that potential hormonal effectors of water and ion transport including vasopressin were inactive may be significant with regard to the physiological role of strial adenylate cyclase.