0000000000243863
AUTHOR
Gabriele Hill
Nitric oxide is formed in a subpopulation of rat pineal cells and acts as an intercellular messenger.
In the rat pineal, formation of the second messenger cyclic GMP (cGMP) is under adrenergic control. Two important sequential steps mediate adrenergic signal transduction by cGMP, receptor-stimulated nitric oxide (NO) formation by the enzyme NO synthase I (NOS I), and NO-induced cGMP formation by the cytosolic enzyme guanylyl cyclase. With regard to the first step in cGMP transduction (i.e. NO formation) we found, by means of NOS I immunostaining and NADPH-diaphorase staining, that the presence of NOS I was restricted to a subpopulation of pineal cells, generally surrounded by NOS I-negative cells. Considering the fact that NO is able to permeate the cell membrane, the question arises whethe…
In rat pinealocytes the cyclic GMP response to NO is regulated by Ca2+ and protein kinase C
There is ample evidence that beta-adrenergic stimulation of cyclic GMP formation is potentiated by alpha1-adrenergic mechanisms, the latter leading to elevation of intracellular Ca2+ concentration ([Ca2+]i) and protein kinase C (PKC) activation. Recent studies have shown that nitric oxide synthase (NOS) and nitric oxide (NO) are a component of the adrenoceptor-cyclic GMP signalling pathway. The aim of the present investigation was to study the roles of alpha1-adrenergic mechanisms, Ca2+ and PKC on NO-stimulated cyclic GMP formation. To this end suspension cultures of rat pinealocytes were treated with the NO donor sodium nitroprusside (SNP) in the presence of alpha1-adrenergic agonists, [Ca…