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Effects of Acid‐base Changes on Human Ureteric Smooth Muscle Contractility
Author(s) -
COLE R. S.,
FRY C. H.,
SHUTTLEWORTH K. E. D.
Publication year - 1990
Publication title -
british journal of urology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 0007-1331
DOI - 10.1111/j.1464-410x.1990.tb14923.x
Subject(s) - contractility , acidosis , extracellular , contraction (grammar) , medicine , chemistry , intracellular , intracellular ph , endocrinology , muscle contraction , biophysics , smooth muscle , stimulation , biology , biochemistry
Summary— Wide fluctuations of both urinary pH and the partial pressure of CO 2 (PCO 2 ) occur in normal physiological circumstances and in a variety of pathological conditions. However, the effect of extracellular pH on the contractility of human ureteric muscle has not been clearly defined. This study has established, using a microsuperfusion technique, that an increased superfusate PCO 2 increases the magnitude of the phasic contraction to electrical field stimulation. A similar extracellular acidosis induced by alteration of the [HCO 3 ‐ ], at constant [Na + ] and free [Ca 2+ ], was without significant effect. Furthermore, when both superfusate PCO 2 and [HCO 3 ‐ ] were simultaneously increased at constant pH the contractile response was similar to that when PC0 2 alone was raised. These observations suggest that the changes of tension were mediated by intracellular pH changes, providing it is assumed that the ureteric smooth muscle cell membrane is permeable to CO 2 but impermeable to H + and HCO 3 ‐ . The occurrence of an increase of force in the presence of an acidosis is a highly significant and unusual finding, since it has been assumed that the classical association between acidosis and negative inotropy, seen in cardiac muscle, was also applicable to smooth muscle.