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Journal of Experimental Biology 140,171-186 (1988)
Published by Company of Biologists 1988

Kinetics of Calcium Fluxes Across the Intestinal Mucosa of the Marine Teleost, Gadus Morhua, Measured Using an In Vitro Perfusion Method

KRISTINA SUNDELL 1 and BJÖRN THRANDUR BJÖRNSSON 2

1 Department of Zoophysiology, University of Göteborg, PO Box 250 59, S-400 31 Göteborg, Sweden
2 Department of Zoophysiology, University of Göteborg PO Box 250 59, S-400 31 Göteborg, Sweden

An in vitro technique for perfusion of the intestinal vasculature and lumen was developed and used to measure calcium (Ca2+) fluxes across the intestinal mucosa of the marine teleost, the Atlantic cod (Gadus morhua). Saturable and nonsaturable components of the calcium influx and efflux were determined.

The calcium influx had one passive component and one saturable component, following Michaelis-Menten kinetics with Km = 8.41mmoll-1 and Vmax = 0.604µmol Ca2+ kg-1 h-1. At physiological Ca2+ concentrations in the vascular ([Ca2+] = l.9mmoll-1) and luminal ([Ca2+] =14.9mmoll-1) perfusion fluids, the saturable component amounted to 60% of the Ca2+ influx. The high-affinity Ca2+-ATPase inhibitor chlorpromazine (CP, 10-4moll-1) antagonized 45% of the Ca2+ influx.

The Ca2+ efflux across the intestinal mucosa of the cod was a saturable process, following Michaelis-Menten kinetics with Km =6.15mmoll-1 and Vmax =3.79µmol Ca2+ kg-1h-1, but insensitive to CP (l0-5moll-1) . The Ca2+ efflux was l.22µumol Ca2+ kg-1 h-1, representing about 20% of the total calcium excretion and about 50% of the extrarenal excretion of the Atlantic cod in vivo.

Key words: Ca2+, Ca2+influx, perfusion, chlorpromazine, Atlantic cod, in vitro, intestine

Accepted on April 20, 1988






© The Company of Biologists Ltd 1988