THE EFFECT OF BILE SALTS ON CONTRACTILITY AND CALCIUM DEPLETION OF POLARIZED AND DEPOLARIZED SMOOTH MUSCLE

¹ Department of Physiology, University of Western Australia, Nedlands, Western Australia

Bile salts had a generalized, reversible inhibitory effect on isometric contractile responses of polarized and depolarized visceral smooth muscle. In polarized muscle, contractions with drugs, chemical or electrical depolarization were rapidly inhibited but response to high-strength longitudinal a.c. was unaffected. These results suggested a superficial membrane effect and were also shown by another steroid, testosterone, and by an anionic detergent. In depolarized muscle, longer exposures to bile salts reversibly blocked contractions with longitudinal a.c. at high field strength, suggesting a secondary deeper effect. This was not shared, however, by testosterone or detergent. Bile salts and testosterone, but not anionic detergent, blocked calcium contractures of calcium-depleted, depolarized muscle.

Bile salts did not affect the rate of loss of total tissue calcium in calcium-free NaCl Ringer solution but significantly enhanced the rate in calcium-free depolarizing (K₂,SO₄) solution.