AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 1 124-R131, Copyright © 1993 by American Physiological Society

ARTICLES

Single-pass gill extraction and tissue distribution of atrial natriuretic peptide in trout

K. R. Olson and D. W. Duff
Indiana University School of Medicine, South Bend Center, University of Notre Dame 46556.

A new method is described in the present experiments to quantify atrial natriuretic peptide (125I-ANP) extraction from plasma in a single transit through the gill vasculature of an unanesthetized trout. Tissue distribution of 125I relative to an inert extracellular space marker, 58Co-EDTA, was also measured 1 h after injection of 125I-ANP. Single-pass extraction of 125I-ANP by the gill was 60% in control fish; it fell to 18% in fish previously injected with saline and became negative (relative to 58Co-EDTA) after treatment with the clearance (C-type) receptor inhibitor SC 46542. Approximately 90% of a 125I-ANP bolus injected into control trout is removed from the circulation within 2 min. 125I concentration in gill tissue was nearly seven times greater than that predicted by the 58Co-EDTA space. 125I was also concentrated in brain (2X), gallbladder, gastrointestinal tract, and eye (all 1X). SC 46542 decreased gill 125I binding from seven times to one times the 58Co-EDTA space and increased 125I accumulation in heart, kidney, fat, and skeletal muscle. Extraction of 125I-ANP by the isolated perfused gill was 53%, similar to that observed in vivo. These results show that the gill is a major site for ANP removal from trout plasma and that C-type receptors are predominant in this process.

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