Korean J Physiol Pharmacol.  2005 Apr;9(2):103-108.

Regulation of L-type Calcium Channel Current by Somatostatin in Guinea-Pig Gastric Myocytes

• Kim YC
• Sim JH
• Lee SJ
• Kang TM
• Kim SJ
• Kim SR
• Youn SJ
• Lee SJ
• Xu WX
• So I
• Kim KW

Abstract

To study the direct effect of somatostatin (SS) on calcium channel current (IBa) in guinea-pig gastric myocytes, IBa was recorded by using whole-cell patch clamp technique in single smooth muscle cells. Nicardipine (1microM), a L-type Ca2+ channel blocker, inhibited IBa by 98+/-1.9% (n=5), however IBa was decreased in a reversible manner by application of SS. The peak IBa at 0 mV were decreased to 95+/-1.1, 92+/-1.9, 82+/-4.0, 66+/-5.8, 10+/-2.9% at 10-10, 10-9, 10-8, 10-7, 10-5 M of SS, respectively (n=3~6; mean+/-SEM). The steady-state activation and inactivation curves of IBa as a function of membrane potentials were well fitted by a Boltzmann equation. Voltage of half-activation (V0.5) was -12+/-0.5 mV in control and -11+/-1.9 mV in SS treated groups (respectively, n=5). The same values of half-inactivation were -35+/-1.4 mV and -35+/-1.9 mV (respectively, n=5). There was no significant difference in activation and inactivation kinetics of IBa by SS. Inhibitory effect of SS on IBa was significantly reduced by either dialysis of intracellular solution with GDPbetaS, a non-hydrolysable G protein inhibitor, or pretreatment with pertussis toxin (PTX). SS also decreased contraction of guinea-pig gastric antral smooth muscle. In conclusion, SS decreases voltage-dependent L-type calcium channel current (VDCCL) via PTX- sensitive signaling pathways in guinea-pig antral circular myocytes.

Keyword

Gastric myocytes; Calcium current; Somatostatin; G-protein

MeSH Terms

Calcium Channels
Calcium Channels, L-Type*
Dialysis
GTP-Binding Proteins
Kinetics
Membrane Potentials
Muscle Cells*
Muscle, Smooth
Myocytes, Smooth Muscle
Nicardipine
Pertussis Toxin
Somatostatin*
Calcium Channels
Calcium Channels, L-Type
GTP-Binding Proteins
Nicardipine
Pertussis Toxin
Somatostatin