Prostaglandin production by the guinea-pig endometrium: is calcium necessary?

The output of prostaglandin (PG) F2 alpha from guinea-pig endometrium obtained on day 15 of the oestrous cycle and maintained in tissue culture was significantly (P less than 0.05) reduced by the use of Ca2+-depleted medium, EGTA (a Ca2+ chelator), 8-(N,N-diethyl-amino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8; an intracellular Ca2+ antagonist), trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7; both calmodulin antagonists). Nifedipine inhibited PGF2 alpha output at a concentration (100 mumol/l) much greater than that usually required to block Ca2+ channels. Verapamil had a small but significant (P less than 0.05) inhibitory effect on PGF2 alpha output at 10-100 mumol/l. The outputs of PGE2 and, to a lesser extent, 6-keto-PGF1 alpha (the hydrated product of PGI2) were also reduced by using Ca2+-depleted medium. EGTA reduced the outputs of PGE2 and 6-keto-PGF1 alpha on day 1 of culture, but stimulated 6-keto-PGF1 alpha output on day 3 of culture. The outputs of PGE2 and 6-keto-PGF1 alpha were increased by TMB-8 (100 mumol/l) on day 3 of culture and by TFP and, to a smaller extent, by W-7 on all 3 days of culture. Nifedipine (100 mumol/l by not 1 or 10 mumol/l) reduced the outputs of PGE2 and 6-keto-PGF1 alpha on all 3 days of culture, whereas verapamil (100 mumol/l but not 1 or 10 mumol/l) increased the outputs of these two prostaglandins on days 2 and 3 of culture.(ABSTRACT TRUNCATED AT 250 WORDS)