Angiotensin II increases intracellular calcium concentration in pig endometrial stromal cells through type 1 angiotensin receptors, but does not stimulate phospholipase C activity or prostaglandin F2α secretion

Abstract

Although the presence of endometrial receptors for angiotensin (Ang) II has been demonstrated, a specific function for AngII in the uterus has not been identified. Cytosolic free Ca2+ concentration [Ca2+]i, phospholipase C (PLC) activity and prostaglandin (PG) F2α secretion in response to AngII and oxytocin (OT) were measured in pig endometrial stromal cells collected 16 days after oestrus. Treatment with 100 nm OT or AngII increased (P<0.001) [Ca2+]i in stromal cells similarly (720 v. 690 m, respectively). Subsequent administration of OT or AngII to the same cells induced smaller [Ca2+]i increases (25% or 35% of the initial responses, respectively) that occurred only if the second exposure to the same agent took place at least 5 min after the first. When administered sequentially, OT and AngII each induced a full response within 1 min of the previous treatment, regardless of which peptide was applied first. Whereas OT increased PLC activity and PGF2α secretion in stromal cells (P<0.01), AngII did not increase either PLC activity or PGF2α secretion. Type 1 AngII (AT1) receptors were present on stromal cells, whereas AT2 receptors were absent. Therefore, the effect of AngII in stromal cells was mediated via AT1 receptors. That AngII increased [Ca2+]i in stromal cells, but did not increase PLC or PGF2α secretion, indicates that either AngII releases a pool of Ca2+ through a mechanism that is not mediated by PLC and is not involved in PGF2α secretion or that a mechanism for PGF2α production other than one involving Ca2+ may exist.