Variegated effects of prostaglandins on spontaneous activity in bovine mesenteric lymphatics

Abstract

The effects of PGs (PGA 2, PGB 2, PGE 2, PGF 2α, PGI 2, and 6-keto PGF 1α) were investigated quantitatively in insolated bovine mesenteric lymphatics for elucidating the possible significance of PGs in lymph propulsion. 10 −8 M PGF 2α, PGA 2, and PGB 2 produced recognizable increases of frequency and amplitude of spontaneous contractions. The positive chrono-and inotropic responses were enhanced with increasing concentration of the PGs from 10 −8 to 10 −6 M. Both PGE 2 and PGI 2 in a concentration range from 10 −8 to 10 −6 M caused dose-related reductions in the amplitude of spontaneous contractions. No decrease in contraction rhythm was observed by the administration of PGI 2 and PGE 2 at concentrations lower than 5 × 10 −7 M. All of the above-mentioned responses induced by PGF 2α, PGA 2, PGB 2, PGI 2, and PGE 2 were not inhibited by pretreatment with α- and β-adrenergic blocking agents, muscarinic antagonist, antihistamics, and serotonic antagonist. These findings suggest that PGF 2α, PGA 2, and PGB 2 in a low concentration may facilitate lymph flow of bovine mesenteric lymphatics in the living body, since the spontaneous contractions of lymphatic smooth muscle may drive lymph centripetally in the presence of direction valves. On the other hand, PGI 2 and PGE 2 may cause an inhibition of lymph transport.