Transcapillary exchange in the cat salivary gland during secretion, bradykinin infusion and after chronic duct ligation.

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Abstract
1. Capillary permeability‐surface area products for 86Rb, [51Cr]EDTA (mol. wt. 357), [57Co]cyanocobalamin (mol. wt. 1353) and [125I]insulin (approximate mol. wt. 6000) have been measured using the single‐circulation, multiple‐tracer dilution technique in the in situ perfused submandibular salivary gland during parasympathetic nerve stimulation, close‐arterial bradykinin infusion and following chronic duct ligation. 2. In glands with a natural blood supply, permeability‐surface area for 86Rb and [51Cr]EDTA increased during parasympathetic stimulation, but this was shown to be related to the concomitant increase in blood flow rather than to a change in capillary permeability or in surface area. 3. In glands perfused at constant flow, parasympathetic stimulation led to a decrease in permeability‐surface area for EDTA (‐19.1 +/‐ 5.2%, mean +/‐ S.E., n = 5, P less than 0.05) cyanocobalamin (‐12.3 +/‐ 6.0, n = 12, P less than 0.05), and insulin (‐15.3 +/‐ 4.8, n = 11, P less than 0.02). It is suggested that this may be the result of a redistribution of flow from the acinar microcirculation to a less permeable ductal vasculature. 4. Bradykinin infusion had no significant effect on permeability‐surface area for EDTA and cyanocobalamin in perfused glands. 5. In perfused glands, ligation of the submandibular duct for 3‐‐12 days reduced permeability‐surface area (ml.min‐1.g‐1) for [51Cr]EDTA from 5.26 +/‐ 0.60 (mean +/‐ S.E., n = 9) to 4.20 +/‐ 0.12 (n = 4, P less than 0.30), [57Co]cyanocobalamin from 3.22 +/‐ 0.12 (n = 48) to 2.02 +/‐ 0.08 (n = 15, P less than 0.001) and [125I]insulin from 1.52 +/‐ 0.07 (n = 39) to 0.72 +/‐ 0.23 (n = 11, P less than 0.001).