An antihypertensive substance associated with erythrocytes.

An extract was prepared from hemolyzed erythrocytes of spontaneously hypertensive rats (SHR) which inhibits lanthanum-resistant calcium uptake by aortic segments and lowers blood pressure in several models of hypertension. Erythrocyte hemolysates were extracted with Triton X-100 and partially purified by boiling and Sephadex G-150 column chromatography. The effects of the extract on calcium uptake by aortic segments in vitro were reversible and dose dependent. The extract was administered by intraperitoneal injection to male and female SHR, deoxycorticosterone-NaCl hypertensive rats (DOCA-NaCl), one-kidney one-clip (1K,1C) and two-kidney, one-clip (2K,1C) renovascular hypertensive rats, and their appropriate control groups. At 24 h postinjection, the antihypertensive factor (AHF) lowered the systolic blood pressure (SBP) in the conscious SHR male (200 +/- 7 to 132 +/- 11 Torr), SHR female (172 +/- 4 to 117 +/- 11), DOCA-NaCl (187 +/- 6 to 121 +/- 8), 2K,1C (165 +/- 8 to 127 +/- 7), and 1K,1C (167 +/- 8 to 146 +/- 13) models of hypertension. The duration of the effect on the SBP was model dependent. The SBP was significantly decreased for 4-8 days in SHR, 4 days in 1K,1C and 2K,1C, and 2 days in DOCA-NaCl. In contrast to the results obtained in hypertensive rats, AHF had little effect on the SBP of normotensive animals. Both the blood pressure and calcium effects were abolished by digestion with phospholipase D, tentatively suggesting that the compound(s) inducing these effects may be a phospholipid or have a phospholipid moiety.