Hormonal factors influencing intestinal lymph flow

Lawrence, Catherine Jo-Anne (1980) Hormonal factors influencing intestinal lymph flow. Masters thesis, Memorial University of Newfoundland.

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Abstract

Splanchnic blood flow is known to increase in the postprandial state though the mechanisms are unclear. Gut hormones are probably at least partially responsible. Intestinal lymph is mainly derived from the splanchnic blood via capillary filtration. As alterations in the slpanchnic microcirculation are likely to be associated with alterations in intestinal lymph flow this study was devised to examine the effects of two hormones, namely secretin and vasoactive intestinal polypeptide, on intestinal lymph flow and composition. -- Conscious restrained male Sprague-Dawley rats with intestinal lymphatic fistulae, duodenal cannulae, and tail-vein cannulae were studied. -- Natural secretin at doses from 0.25 - 5 U/ml and a saline control were administered intravenously in ten animals. Lymph flow, protein concentration and output were determined. To exclude the possibility of a vasoactive contaminant causing the observed effects, three rats were studied similarly with synthetic secretin. -- Analysis of the results gave polynomial curves with 95% confidence bands for each set of data. Comparison of the equations between natural and synthetic secretin for lymph flow and protein output showed no significant difference (p > .01). These results indicate that secretin is a powerful stimulant of intestinal lymph flow and protein output in the conscious rat. However, the mechanism by which secretin produced these effects is unclear. -- A steady-state of enhanced lymph flow was established. Protein concentration of successive lymph samples taken throughout the infusion showed no measurable change. Examination of gradient polyacrylamide Electrophoretic gels showed no evidence of change in the protein pattern as a result of alterations in lymph flow suggesting that secretin does not alter capillary permeability. It is proposed that secretin may open up previously non-perfused vessels. -- Vasoactive intestinal polypeptide was studied in three animals in which 0.1 µg, 0.5 µg and a saline control were administered. Unlike secretin, no alteration in intestinal lymph flow or protein output was observed. -- In conclusion, while natural and synthetic secretin are potent intestinal lymphagogues, vasoactive intestinal polypeptide seems to have no intestinal lymphagogue effect.

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