Mechanisms Of Blood Pressure Regulation Research Articles

The release of vasopressin in response to haemorrhage and its role in the mechanism of blood pressure regulation.

1. The release of vasopressin in response to haemorrhage and the effects of vasopressin infusions on blood pressure and heart rate have been investigated in anaesthetized dogs. Haemorrhage was produced by the method of Lamson & de Türk (1945), which allows for a precise control of the changes in arterial blood pressure.2. Blood samples were collected from an external jugular vein, from a femoral vein or from a femoral artery and extracted with alcohol; blood extracts were assayed for antidiuretic activity.3. Haemorrhage experiments showed that vasopressin secretion is increased when the fall in diastolic blood pressure (diastolic DeltaP) is 25 mm Hg or more. Mild hypotensions (diastolic DeltaP ranging from 21 to 30 mm Hg) produce an average fourfold increase in the concentration of vasopressin in blood. Such increase is maintained throughout the oligaemic period. Severe hypotensions produce, in most cases, a biphasic secretory response, with an initial high peak followed by a lower, constant, secretory plateau. In all experiments, the retransfusion of blood restored vasopressin to control levels.4. Vasopressin infusion experiments showed that the amounts of hormone secreted in response to haemorrhage are sufficient to cause vasopressor response, provided that the buffering action of blood pressure regulation mechanisms is suppressed. It was also found that the amounts of vasopressin secreted in response to haemorrhage are apparently adequate, if the function of such secretion is to combat the hypotension which follows haemorrhage.5. The effect of hypophysectomy on the blood pressure of animals previously submitted to bilateral division of the vagi and sinus nerves (deafferented animals) was also investigated. It was found that hypophysectomy is followed by a fall in arterial blood pressure which is positively correlated to the previous existing amounts of vasopressin. The time course of this hypotension is similar to that following the stopping of an infusion in a deafferented hypophysectomized animal. In some experiments it was shown that, following hypophysectomy, blood pressure can be restored to its pre-hypophysectomy level by an adequate infusion of vasopressin.6. It is proposed that the release of vasopressin in response to stimuli arising from cardiovascular sensory receptors plays a part in the mechanism of blood pressure regulation.

Studies on Morbidity and Familial Aggregation of Cerebrovascular Disease among Hypertensives

An investigation was done on the familial aggregation of blood pressure levels and the incidence of cerebrovascular diseases in the families of 257 pupils of both sexes at a high school in an inland farm area of the northeast part of Japan. The examination consisted from the items of blood pressure measurement, cold pressor test, electrocardiography, ocular fundus examination, urinary tests and measurements of stature. These data were compared between family groups of hypertensives and normotensives. 1. Polygenic mechanism for blood pressure regulation was suggested by normal distribution of blood pressure levels of the pupils, sex and age adjusted scores and the logarithmic converted blood pressures of the families. 2. Incidence of hypertensive pupils was significantly higher from hypertensive parents than from normotensive ones. The same tendency was established for the morbidity of hypertensives for the parents that the higher the blood pressure levels of the grand-parents the larger the incidence for the parents of the pupils. 3. The blood pressure levels, incidences of myocardial injuries and of cerebrovascular diseases were significantly higher for the group of the grand-parents of the hypertensive parents. However, the tendency was not seen for the group of grandfathers if divided to male and female subgroups. 4. Parent-child relationship indicated by regression coefficient of the sex-age-adjusted systolic blood pressures was almost near 0.0 between the male pupils and their fathers, also between the fathers and the grandfathers. However, the coefficients were about 0.2 and significant between the sets of the daughters and the fathers, the daughters and the mothers, and the sons and the mothers. 5. These findings reveal that familial aggregation of the blood pressure levels is influenced by maternal effects. This might mean that the effects of social and economic conditions of the families are more consistent than the biological inheritance.

Interrelation between central and peripheral mechanisms regulating blood pressure.

Electrical stimulation of selected discrete sites in the diencephalon induced a profound and coordinated response consisting of increased respiratory activity, limb movements, and cardiovascular adjustments. The effects on the cardiovascular system were similar to those of exercise, although the increases in aortic pressure, left ventricular pressure, and heart rate were greater. Massive splanchnicnerve discharge occurred immediately when the diencephalon was stimulated, but splanchilic activity abruptly fell below control levels with cessation of the stimulus. The increase in respiratory activity and the organized running movements seen during stimu lation apparently did miot contribute to the pressor and cardioaccelerator responses. There appeared to be no marked difference between control and diencephalic-stimulation experiments in the ease with which in duced pressure pulsations in the partially isolated carotid sinus caused bradycardia and blood-pressure depression. It may be that the influences of the diencephalon and carotid- sinus reflex upon blood pressures are inde pendent and sum algebraically. Experiments in which effects of epinephrine on splanchnic-nerve activity and systemic arterial pressure were measured before and during dieneephalic stimulation did not support the concept that catecholamines have an important role in normal pressor responses.

自律神経機能調節機構(V)

自律神経機能調節機構(V)

Method for studying competence of the body's blood pressure regulatory mechanisms and effect of pressoreceptor denervation.

Method for studying competence of the body's blood pressure regulatory mechanisms and effect of pressoreceptor denervation.