Phosphoinositide breakdown in isolated rat parotid membranes. Stimulation by cholinergic and alpha-adrenergic agonists |
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Authors: | E Nadler M S Nijjar Y Oron |
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Affiliation: | Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-01, Japan |
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Abstract: | Parotid gland membranes labelled with [3H]inositol were challenged with the cholinergic agonist, carbamylcholine, or with epinephrine in the presence of propranolol. Both agonists caused a significant breakdown of labelled phosphoinositides (17.5%) in membranes suspended in Krebs-Ringer bicarbonate buffer. This effect was abolished by the respective antagonists, atropine or phentolamine. The carbamylcholine-induced breakdown of labelled phosphoinositides did not require cytosol. The addition of cytosol alone, or the exposure of membranes to a medium of low ionic strength caused a significant breakdown of phosphoinositides (10-40%). No further breakdown due to the addition of carbamylcholine was observed under these conditions. It is suggested that neurotransmitter-induced breakdown of phosphoinositides is effected by membrane-associated enzyme(s) and can be observed only in a medium of high ionic strength. |
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Keywords: | Brain Carrot Cell culture Colchicine Podophyllotoxin Tubulin |
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