Modulation of Angiotensin II Type 1 Receptor mRNA Expression in Human Blood Cells

Comparison of Platelets and Mononuclear Leucocytes

Abstract

The objective of the present study was to quantify the expression of angiotensin II type 1 (AT1) receptor transcripts in human blood cells-platelets and mononuclear leucocytes-from 10 normal healthy volunteers during the alterations in the renin-angiotensin system. A quantitative assay employing reverse transcription-polymerase chain reaction (RT-PCR) was utilized. Oral administration of furosemide, 40mg for 2 days, under mild salt restriction (50mEq NaCl/day) for 6 days stimulated the rennin-angiotensin system resulting in significant increases in plasma renin activity (PRA) (1.84±0.12vs. 1.05± 0.17ng/l/s; P<0.01), plasma angiotensin II concentration, and plasma aldosterone concentration (PAC). The ratio of AT1 receptor mRNA to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA expression in mononuclear leucocytes was significantly (P<0.05) increased from the basal level (0.49±0.05 vs. 0.29±0.03) (P<0.01), while in platelets these changes were opposite (0.11±0.05vs. 0.25±0.05) (P<0.01). Compared to these significant changes, salt loading (200mEq NaCl/day) for 6 days decreased PRA(0.49±0.10vs. 1.05±0.17ng/l/s; P<0.01) and induced the opposite changes in the ratio of AT1 receptor/GAPDH mRNA. These data suggest that AT1 receptors in human blood cells may be of two different types-platelets and mononuclear leucocytes.