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We studied the cholinergic stimulation of isolated and enriched rat parietal cells. H+ production was indirectly measured by the uptake of 14C-aminopyrine into the parietal cells. Stimulation by carbachol required the presence of extracellular Ca2+ not only in the initial phase but also during the sustained phase of a 100-min incubation period. The response to carbachol was prevented by the Ca2+ entry blocker lanthanum IC50: 1.5 X 10(-7) mol/l). Furthermore, the dependence on Ca2+ influx of cholinergic stimulation was demonstrated by a 269% increase in total intracellular Ca2+ in response to carbachol, as determined by optical emission spectrometry. The naphthalene sulfonamides W7 and W5 which bind calmodulin and thus block the intracellular transduction of Ca2+ effects also inhibited a carbachol-induced H+ production. In the following experiments we studied the effect of agents which activate the protein kinase C, an enzyme which is supposed to play a key role in intracellular signal transduction of Ca2+-dependent effects. Phospholipase C is supposed to activate protein kinase C via induction of the phosphoinositol breakdown. In our preparation of isolated rat parietal cells, phospholipase C (4-100 mU/ml) exerted inhibition instead of amplification of the response to 10(-4) mol/l carbachol. Similarly, the direct activation of protein kinase C by 12-O-tetradecanoylphorbol-13-acetate or by 1-oleoyl-2-acetyl-sn-glycerol (both tested at 10(-7) to 10(-5) mol/l) reduced the submaximal and maximal response to 10(-5) or 10(-4) mol/l carbachol. We conclude that the cholinergic stimulation of rat parietal cells is dependent on the influx of extracellular Ca2+. Calmodulin seems to mediate intracellular Ca2+ effects during cholinergic stimulation. The activation of protein kinase C impairs carbachol-induced H+ production instead of augmenting the response. This might be due to an already maximal activation of protein kinase C by carbachol alone or to autoregulatory down-regulation by the protein kinase C of muscarinic parietal-cell receptors.
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
July 1981,
The Journal of clinical investigation,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
May 1997,
Zhongguo yao li xue bao = Acta pharmacologica Sinica,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
October 1991,
Nihon Shokakibyo Gakkai zasshi = The Japanese journal of gastro-enterology,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
November 1987,
Biochemical and biophysical research communications,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
April 1996,
The American journal of physiology,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
February 1981,
Life sciences,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
May 1999,
International journal of molecular medicine,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
August 1994,
FEBS letters,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
November 1998,
The Journal of endocrinology,
W Schepp, and
E Brosch, and
C Tatge, and
V Schusdziarra, and
M Classen
December 1989,
The Biochemical journal,
