cAMP directly facilitates Ca-induced exocytosis in bovine lactotrophs.
We have used the whole cell patch clamp technique on single prolactin-secreting bovine lactotrophs to measure plasma membrane capacitance (Cm), an index of membrane surface area, under voltage-clamp during cytosol dialysis with Ca and cAMP. cAMP increased the magnitude and rate of Ca-induced exocytosis (Cm increase) without affecting membrane conductance; however, cAMP had no detectable effect on Cm when intracellular Ca was low. We thus report new evidence that cAMP can facilitate Ca-induced secretion in a synergistic fashion, by acting directly on the secretory apparatus, independently of membrane conductance activation.
Sikdar
S K
SK
Department of Neuroendocrinology, AFRC Institute of Animal Physiology, Cambridge, UK.
Zorec
R
R
Mason
W T
WT
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D005089:Exocytosis / Q000187:drug effects*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*
D004533:Egtazic Acid; D011388:Prolactin; D000242:Cyclic AMP; D002118:Calcium