Martin D S, Rodrigo M C, Appelt C W
Department of Physiology and Pharmacology, University of South Dakota School of Medicine, Vermillion 57069-2390, USA.
Hypertension. 1998 Jan;31(1):139-44. doi: 10.1161/01.hyp.31.1.139.
The initial stages of hypertension in the spontaneously hypertensive rat (SHR) are characterized by an increase in cardiac output. Venous capacitance plays an important role in the control of cardiac output. This study tested the hypothesis that venous tone is elevated in the developmental stages of spontaneous hypertension. Male SHR or normotensive Wistar-Kyoto (WKY) rats were instrumented for the measurement of arterial pressure (FAP) and intrathoracic vena caval pressure (FVP). A latex-tipped catheter was advanced into the right atrium via the jugular vein. Mean circulatory filling pressure (MCFP), an index of integrated venomotor tone, was calculated as MCFP=FVP+(FAP-FVP)/VAR. FAP and FVP were recorded after 5 seconds of right atrial balloon inflation. The venous to arterial compliance ratio (VAR) was estimated as 76 for WKY and 106 for SHR. Mean arterial pressure (MAP), heart rate, and MCFP were recorded in conscious rats of 4 to 6 and 8 to 10 weeks of age. In 4- to 6-week-old rats, both MAP and MCFP were significantly elevated in the SHR (MAP, 129+/-6 mm Hg; MCFP, 6.6+/-0.4 mm Hg) compared with the age-matched WKY (MAP, 91+/-6 mm Hg; MCFP, 5.4+/-0.4 mm Hg), whereas heart rate was not significantly different. The elevations in MAP (SHR, 144+/-4 mm Hg; WKY, 102+/-3 mm Hg) and MCFP (SHR, 7.7+/-0.3 mm Hg; WKY, 6.0+/-0.2 mm Hg) in SHR were exaggerated at 8 to 10 weeks of age. After ganglionic blockade (chlorisondamine; 10 mg/kg), the differences in MCFP were no longer statistically significant between SHR and WKY at both 4 to 6 weeks of age (3.9+/-0.2 versus 4.0+/-0.3 mm Hg) and 8 to 10 weeks of age (5.0+/-0.3 versus 4.3+/-0.3 mm Hg, respectively). The differences in MAP at 4 to 6 weeks of age (79+/-7 versus 67+/-5 mm Hg, respectively) also were not statistically significant after ganglionic blockade. However, a significant difference in MAP between strains remained after ganglionic blockade in 8- to 10-week-old rats (90+/-5 versus 63+/-3 mm Hg, respectively). These findings indicate that venous tone is increased via autonomic effector systems during the developmental stages of spontaneous hypertension. These data also suggest that autonomic mechanisms predominate at very early stages, whereas nonautonomic mechanisms assume more importance in maintaining the elevated MAP as hypertension progresses.
自发性高血压大鼠（SHR）高血压的初始阶段表现为心输出量增加。静脉容量在控制心输出量方面起着重要作用。本研究检验了自发性高血压发展阶段静脉张力升高的假说。对雄性SHR或血压正常的Wistar-Kyoto（WKY）大鼠进行仪器植入，以测量动脉压（FAP）和胸内腔静脉压（FVP）。将一根带乳胶头的导管经颈静脉推进右心房。平均循环充盈压（MCFP）是综合静脉运动张力的指标，计算方法为MCFP = FVP +（FAP - FVP）/VAR。在右心房球囊充气5秒后记录FAP和FVP。WKY大鼠的静脉与动脉顺应性比值（VAR）估计为76，SHR大鼠为106。记录4至6周龄和8至10周龄清醒大鼠的平均动脉压（MAP）、心率和MCFP。在4至6周龄的大鼠中，与年龄匹配的WKY大鼠（MAP，91±6 mmHg；MCFP，5.4±0.4 mmHg）相比，SHR大鼠的MAP和MCFP均显著升高（MAP，129±6 mmHg；MCFP，6.6±0.4 mmHg），而心率无显著差异。在8至10周龄时，SHR大鼠的MAP（SHR，144±4 mmHg；WKY，102±3 mmHg）和MCFP（SHR，7.7±0.3 mmHg；WKY，6.0±0.2 mmHg）升高更为明显。在进行神经节阻断（氯异吲哚铵；10 mg/kg）后，4至6周龄（3.9±0.2对4.0±0.3 mmHg）和8至10周龄（5.0±0.3对4.3±0.3 mmHg）的SHR和WKY大鼠之间MCFP的差异不再具有统计学意义。4至6周龄时MAP的差异（分别为79±7对67±5 mmHg）在神经节阻断后也无统计学意义。然而，在8至10周龄的大鼠中，神经节阻断后不同品系间MAP仍存在显著差异（分别为90±5对63±3 mmHg）。这些发现表明，在自发性高血压的发展阶段，静脉张力通过自主效应系统增加。这些数据还表明，自主机制在非常早期占主导地位，而随着高血压进展，非自主机制在维持升高的MAP方面变得更加重要。
