Effects of methoxamine and barium on 45Ca2+ fluxes in the rat vas deferens.
The aim of this study was to determine whether methoxamine and barium stimulate 45Ca2+ uptake or efflux in the rat vas deferens in a manner that correlates with their contractile activity, and whether 45Ca2+ movements are inhibited by verapamil or nifedipine. Basal La(3+)-resistant (cellular) 45Ca2+ uptake was significantly greater in the epididymal half (791 +/- 27 nmol g-1) than in the prostatic half (654 +/- 14 nmol g-1) of the rat vas deferens and was unaffected by verapamil (61 microM) or nifedipine (14 microM). Methoxamine (8 microM) was without effect on 45Ca2+ uptake in either half but BaCl2 (1 mM) increased 45Ca2+ uptake by 31% in the prostatic half and by 22% in the epididymal half. The barium-induced increases in 45Ca2+ uptake were markedly reduced or abolished by verapamil (2 microM) or nifedipine (0.3 microM), which at these concentrations have no effect on the rhythmic contractions but abolish the initial small phasic contraction induced by barium. The basal rate of 45Ca2+ efflux from the intact vas deferens (into Ca2+ containing Krebs-Henseleit solution or into Ca-free Krebs-Henseleit solution +/- EGTA 0.05 mM) was not affected by verapamil (61 microM) or nifedipine (14 microM). Methoxamine (8 microM) produced a marked, transient and reversible increase in 45Ca2+ efflux into 2.5 mM CaCl2 Krebs-Henseleit in 50% of the intact vasa deferentia examined which was augmented by verapamil (61 microM). BaCl2 (1 mM) produced a small increase in 45Ca2+ efflux into Ca(2+)-containing and Ca(2+)-free Krebs-Henseleit solutions from some intact vasa deferentia and this was not inhibited by nifedipine (14 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
Hay
D W
DW
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, Scotland, UK.
Wadsworth
R M
RM
D000818:Animals; D001464:Barium / Q000494:pharmacology*; D017609:Barium Compounds; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides; D008297:Male; D008729:Methoxamine / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014649:Vas Deferens / Q000187:drug effects* / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
D017609:Barium Compounds; D002712:Chlorides; C024986:barium chloride; D001464:Barium; D014700:Verapamil; D008729:Methoxamine; D009543:Nifedipine; D002118:Calcium