Process of re-establishment of beta-adrenergic induced protein secretion after cytochalasin D inhibition in rat parotid gland. Effect of cholinergic agonist, phorbol ester and calcium.
In rat parotid gland, 3H-protein secretion is stimulated by beta-adrenergic receptor activation (via cAMP) and also by cholinergic receptor activation (via IP3, calcium and diacylglycerol). The disorganization of microfilament system by cytochalasin D induced an inhibition of beta-adrenergic induced 3H-protein secretion whereas it did not modify the cholinergic muscarinic one. Cytochalasin D induced the formation of vacuoles in the parotid cell. In this work we show that the activation of muscarinic receptors (with carbachol) partially abolished the inhibitory effect of cytochalasin D on beta-adrenergic induced secretion. Since carbachol induced both intracellular calcium increase and protein kinase C activation, we decided to test separately the effect of calcium (using the calcium ionophore A23187) and protein kinase C activation (using phorbol ester) on the inhibitory effect of cytochalasin D on beta-adrenergic induced secretion. A23187, in the presence of calcium in the external medium was able to partially abolish cytochalasin D effect (ie re-establishing protein secretion) whereas activation of protein kinase C by phorbol 12-13 di-butyrate had no effect. These results suggest that protein kinase C is not involved in re-establishing a 'normal' secretion phenomenon whereas calcium does interfere. Furthermore, our fluorescence study shows that, when cytochalasin D is present in the incubation medium, the actin network is disturbed even in the presence of carbachol. This indicates that a calcium entry in the cell is not sufficient to restore a 'normal' actin network.(ABSTRACT TRUNCATED AT 250 WORDS)
Huleux
C
C
Biochimie des transports cellulaires, CNRS URA 1116, Université Paris XI, Orsay, France.
Dreux
C
C
Lemullois
M
M
Rossignol
B
B
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010306:Parotid Gland / Q000502:physiology*; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D015398:Signal Transduction; D013268:Stimulation, Chemical
D010703:Phorbol Esters; D011506:Proteins; D015638:Cytochalasin D; D000001:Calcimycin; D002217:Carbachol; D011493:Protein Kinase C; D007545:Isoproterenol; D002118:Calcium