Polymorphonuclear leukocyte membrane fluidity and cytosolic Ca2+ content at baseline and after activation in essential hypertension

Abstract

Obiective: To examine in essential hypertension (EH) the polymorphonuclear leukocyte (PMN) membrane fluidity and cytosolic Ca2+ content at baseline and after in vitro activation. Subjects and methods: In 45 hypertensive subjects (27 men and 18 women; mean age 45.8 +/- 11.3 years) we evaluated the PMN membrane fluidity, obtained by labeling PMNs with 1-[4-(trimethyImino)phenyl]-6phenyl-1,3,5-hexatriene (TMA-DPH) and considering the TMA-DPH polarization degree, inversely related to the membrane fluidity, and the PMN cytosolic Ca2+ content, obtained by marking PMNs with Fura 2-AM. These PMN parameters were examined at baseline and after in vitro activation (prolonged for 5 min) with two agents: 4-phorbol 12-myristate 13-acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP). Results: In hypertensives, at baseline we observed a slight decrease of the PMN membrane fluidity and a marked increase of the PMN cytosolic Ca2+ content in comparison with normal subjects. In normal as well as in hypertensive subjects, after activation with both agents (PMA and fMLP), no variation was found in membrane fluidity and cytosolic Ca2+ content. Conclusions: Our data show a basal alteration of the PMN membrane fluidity and Ca2+ content that reflects PMN activation. The latter explains the organ injury accompanying this clinical condition. The absence of variations observed after in vitro activation could depend on the pre-existing spontaneous activation observed in PMNs of hypertensive subjects.