Modulation of angiotensin II type 1 receptor mRNA expression in human blood cells: comparison of platelets and mononuclear leucocytes.

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 leukocytes--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, 40 mg for 2 days, under mild salt restriction (50 mEq NaCl/day) for 6 days stimulated the renin-angiotensin system resulting in significant increases in plasma renin activity (PRA) (1.84 +/- 0.12 vs. 1.05 +/- 0.17 ng/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 +/- 0.05 vs. 0.25 +/- 0.05) (P < 0.01). Compared to these significant changes, salt loading (200 mEq NaCl/day) for 6 days decreased PRA(0.49 +/- 0.10 vs. 1.05 +/- 0.17 ng/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.