Cyclic amp and adenylate cyclase in the inner ear

Abstract

The activity of adenylate cyclase and the steady state levels of cyclic AMP (cAMP) were determined in stria vascularis (SV) and organ of Corti (OC) of the guinea pig cochlea. The activities are 12 and 19 pmoles/mg dry weight/minute for OC and SV, respectively. The activity was increased two to four-fold by NaF. The base level of cAMP is 4.2 and 4.4 nmoles/g dry weight in OC and SV, respectively. In contrast to brain, neither ischemia nor barbiturates produced major changes of the steady state levels of cAMP. No in vitro effect of cAMP upon the state of activation of glycogen phosphorylase was noticeable in either tissue. cAMP did not exert a significant in vitro inhibition of strial Na+K+-ATPase. Perilymphatic perfusion of cAMP (10-3 M) and of theophylline (5 times 10-3 M) did not produce changes in the endolymphatic potential (EP), but dibutyryl cAMP (10-3 M) led to a significant increase of EP. The alpha adrenergic blocking agent, phentolamine, produced very complex changes of the cochlear potentials. A possible role of catecholamines and cAMP in the secretory phenomena of the SV and in the transduction and/or transmission processes of the auditory sense organ are discussed.

Effects of vasopressin on gene expression in rat inner ear

“…Gnas may couple Gprotein coupled receptor binding to AC activation. This result is supported by the previous findings: (1) AC was present in the stria vascularis and semicircular canal epithelium of the inner ear (Ahlstrom et al, 1975;Bagger-Sjoback et al, 1980;Anniko et al, 1981;Mees, 1984;Schacht, 1985;Oudar et al, 1990;Drescher et al, 2000).…”

Endocytosis of MPO in Marginal Cells Is Regulated by PKC, Protein Phosphatase, ERK and PI3-K Signaling Cascades, but Not by PKA and MEK Signaling Cascades

“…Adenylate cyclase stimulator and G-protein activator induced ricin endocytosis via a clathrin-independent mechanism [44] ; however, permanent analogs of cAMP, Bu-cAMP, suppressed fluid-phase endocytosis [19] . It is known that adenylate cyclase is present in the SV of guinea pig [45] . We therefore examined the effect of Bu-cAMP on MPO endocytosis, but could not observe the effects of Bu-cAMP on MPO endocytosis in marginal cells.…”

Sensorineural hearing loss owing to deficient G proteins in patients with pseudohypoparathyroidism: results of a multicentre study

“…Although we still do not know the biological function of the G protein-adenylate cyclase complex in the mammalian inner ear, its existence (mostly in the tissues of the stria vascularis) is certain [9,10,1 I]. According to different authors [9,10,11,29,30], the G protein-adenylate cyclase complex is probably involved in the cochlear ion and fluid balance. So a dysfunction of the inner ear by a hereditary defect of the G protein system could be entirely conceivable.…”