CELL-FREE THYMIC EXTRACT FROM HYPERTENSIVE RATS INDUCES HYPERTENSION IN NORMOTENSIVE RATS

This study examined the role of the thymus in hypertension. Seven to e ight week old, normotensive Wistar-Kyoto rats (WKYs) (systolic blood p ressure 138 +/- 7 mm Hg) received a bolus injection of (1) WKY thymic extract (control), (2) spontaneously hypertensive rat (SHR) thymic ext ract, (3) SHR liver extract or (4) normotensive Sprague-Dawley rat (SD ) thymic extract. Blood pressures of WKYs receiving SHR thymic rose si gnificantly (p < 0.01) over an eight week period (168 +/- 6 mm Hg), wh ile WKYs injected with WKY thymic extract (143 +/- 10), SHR liver extr act (144 +/- 5) or SD thymic extract (138 +/- 4) showed no change in b lood pressure. Thymuses from WKYs injected with SHR extract were signi ficantly (p < 0.01) smaller than thymuses from WKYs injected with WKY extract. Aorta from WKYs administered SHR extract were significantly ( p < 0.01) hyperresponsive to contractile agents, suggesting that immun e dysfunction may lead to vascular damage as seen in several hypertens ive models. The results suggest that hypertension can be transferred v ia an endogenous thymic factor, possibly a viral pathogen.