Immediate and long-term effects of pregnancy on glomerular function in the SHR.

Micropuncture experiments investigated 1) whether a gestational renal vasodilation occurs in the hypertensive gravida and 2) whether pregnancy exposes the spontaneously hypertensive rat (SHR) kidney to increased glomerular blood pressures and thus ultimately to glomerular injury. These studies demonstrate that there is no gestational vasodilation in the midterm pregnant SHR (renal vascular resistance, 30 +/- 2 vs. 30 +/- 3 (mmHg.ml-1.min in midterm pregnant vs. virgin SHR) and, of importance, no difference in glomerular blood pressure in pregnant vs. virgins (54 +/- 1 vs. 55 +/- 1 mmHg). In the long term after three repetitive pregnancies there is no worsening in glomerular function compared with age-matched virgin SHRs (single nephron glomerular filtration rate, 26 +/- 2 vs. 23 +/- 1 nl/min), perhaps not surprising in view of the lack of change in glomerular hemodynamics during a pregnancy. Additional observations indicated that the midterm pregnant, repetitively pregnant, and virgin SHRs have no vasodilatory response to an intravenous amino acid load. Thus the SHR has no acute renal vasodilatory reserve to a glycine infusion and is also unable to undergo a gestational vasodilation. This has no negative impact on either mother or babies and may actually be beneficial to the long-term health of the maternal kidney.