Role of extra- and intracellular ca2+ in the lymphatic myogenic
response.
Atchison, D. J., and M. G. Johnston.
Sunnybrook Health Science Centre and Department of Pathology,
University of Toronto, Toronto, Canada
APStracts 3:0285R, 1996.
Using an actively contracting in vitro preparation of bovine
mesenteric lymph vessels, we studied the effect of selected calcium
channel modulators on the ability of these vessels to propel fluid.
We found that blocking the dihydropyridine receptor with nifedipine
and diltiazem inhibited pumping at concentrations within the range
used clinically (10-7 and 10-6M respectively). Intracellular calcium
modulation using ryanodine (10-6M) also inhibited pumping.
Furthermore, we studied the effect of these agents on the
relationship between lymph flow and transmural pressure; a
relationship normally described by a bell-shaped curve. Diltiazem,
10-6M, attenuated pumping over the range of pressures studied. On the
other hand, ryanodine at 10-7M, a concentration capable of inhibiting
pumping at a constant transmural pressure, had no effect on the
pressure-flow relationship when transmural pressure was manipulated.
Thus we have determined that calcium movement via the L-type channel
contributes significantly to the regulation of lymph pump activity
and that intracellular calcium flux plays a less significant role
that may be modified by transmural pressure.
Received 3 April 1996; accepted in final form 16 July 1996.
APS Manuscript Number R193-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 August 1996