Table 2

Effects of cAMP-elevating agents on the activation of PLD and PLC triggered by ET-1

Pretreatment	cAMP	[³H]PBut		[³H]Inositol Phosphates
Pretreatment	Control	Control	+ ET-1	Control	+ ET-1
	pmol/mg protein	% of total phospholipid		cpm/100 mg of tissue
None	10 ± 2	0.19 ± 0.03	1.42 ± 0.11	14,919 ± 1,193	343,125 ± 27,450
FK	250 ± 21	0.21 ± 0.02	0.82 ± 0.06^2-150	15,963 ± 958	304,784 ± 24,383
dbcAMP		0.24 ± 0.03	0.89 ± 0.07^2-150	17,156 ± 1,887	356,632 ± 42,795
Iloprost	60 ± 3	0.25 ± 0.04	0.84 ± 0.06^2-150	15,665 ± 1,253	324,178 ± 29,176
FK + H89	215 ± 15	0.22 ± 0.03	1.39 ± 0.10
FK + H85		0.23 ± 0.04	0.81 ± 0.07^2-150
C6-ceramide	8 ± 4	0.18 ± 0.04	0.80 ± 0.06^2-150	18,385 ± 1,655	364,137 ± 30,410

For the estimation of the production of [³H]PBut and [³H]inositol phosphates, myometrial strips were prelabeled with [³H]myristic acid andmyo-[2-³H]inositol, respectively. Tissues were then incubated in the absence or the presence of 10 μM forskolin (FK), 1 mM dbcAMP, or 5 μM iloprost for 10 min or 50 μM C6-ceramide for 120 min. When used, H-89 and H-85, both at 30 μM, were added 10 min before forskolin. Butanol (0.3%) (for PLD measurement) and 10 mM LiCl (for PLC measurement) were added during the final 10 min of each treatment. Tissues were stimulated for an additional 10 min with ET-1. [³H]PBut accumulation was expressed as percentage of total label in phospholipid and [³H]inositol phosphate production as cpm/100 mg of tissue. cAMP was estimated as described inMaterials and Methods in separate samples that were submitted to the indicated treatment and was expressed as pmol/mg of protein. Values are the mean ± S.E. of three to five independent experiments, each performed in duplicate.

↵2-150 P < .05 versus ET-1 alone.