Rectal absorption of (Asu1,7)-eel calcitonin in rats.

Abstract

[Asu1, 7]-eel calcitonin ([Asu1, 7]-ECT) was not absorbed well from rat rectum. Although an unstirred layer may exist as a diffusion barrier for [Asu1, 7]-ECT absorption, transport through the epithelial cell membrane is the limiting step for [Asu1, 7]-ECT absorption. Coadministration of 0.33M phenylalanine enamine of ethylacetoacetate (PheEtAA), 0.17M diethylethoxymethylenemalonate (DEEMM), 0.6M sodium salicylate (SA), or 0.05M sodium p-chloromercurylphenyl sulfate (p-CMP) increased the rectal [Asu1, 7]-ECT absorption significantly. In particular, PheEtAA and DEEMM resulted in a more than 180 times greater AUC of [Asu1, 7]-ECT compared to that when [Asu1, 7]-ECT alone was administered rectally, and these two adjuvants were more effective than SA and p-CMP on the rectal [Asu1, 7]-ECT absorption, though all four adjuvants coadministered at the above concentration with sodium cefmetazole caused similar increases of rectal cefmetazole absorption.