Subcellular Ca2+ Mobilization in Gastric Smooth Muscle Contraction

Kim, Kwang Soo; Woo, Nam Sik; Lee, Ye Chul; Kim, Bo Kyung; Kim, Jung Hwan; Cho, Sung Il

Abstract

BACKGROUND: The stomach can be generally classified anatomically into three parts; fundus, corpus, and antrum. It has not been well demonstrated how the three regions contribute to specified gastric motility. In the present study, the regional differences on contractile response and intracellular Ca2+ levels ([Ca2+]i) were investigated in a mouse gastric muscle.
METHODS
An isometrical contraction was measured with a computerized physiograph, and [Ca2+]i was measured with fura-PE3/AM, a fluorescent Ca2+ indicator in gastric smooth muscle from mice.
RESULTS
Carbachol (CCh), a potent muscarinic receptor agonist, generated rhythmic contractions in a dose dependent manner, superimposed on tonic components in the antral muscle. Whereas similar contractile responses to CCh was obtained in the antrum, CCh evoked tonic components predominantly. CCh increased [Ca2+]i in a dose dependent manner in both the antral and fundic smooth muscle. However, the increment of [Ca2+]i in the fundus was greater than that of the antrum. Verapamil (10nM), a l-type Ca2+ channel blocker, inhibited completely the contraction and [Ca2+]i induced by CCh in the antral strips, whereas the responses in the fundus showed a resistance to verapamil.
CONCLUSIONS
These results suggest that muscarinic stimulation has a regional difference on muscle contractility and [Ca2+]i, which is mediated by differences of Ca2+ movement in mouse gastric muscle.