ABSTRACT
Our purpose was to study the influence of the stimulation of the cerebroventricular system on some mechanisms related to hydrosaline equilibrium and blood pressure regulation. Renal function and blood pressure (group 1) as well as the baroreceptor reflex (group 2) were studied. In group 1, we measured diuresis, natriuresis, creatinine clearance, lithium clearance, and blood pressure in control rats and after stimulation of the cerebroventricular system with 1 M NaCl solution. In group 2, we evaluated the baroreceptor reflex, producing an increase of blood pressure with an injection of phenylephrine to obtain baroreceptor reflex curves--characterized by threshold, point of inflection, heart period range, gain, and systolic pressure corresponding to half the heart period range (SBP50)--in control and experimental rats injected with saline and 1 M NaCl solution, respectively. In group 1 experimental rats, we observed a significant increase in diuresis, natriuresis, blood pressure, and glomerular filtration rate. A substantial increase was also registered in sodium filtered load and reabsorbed sodium in the proximal convoluted tubule and distal nephron. No differences were observed either in fractional proximal tubule or in distal nephron sodium reabsorption. In group 2 experimental rats, mean arterial blood pressure, threshold, point of inflection, and SBP50 were significantly higher than in control rats. By contrast, a decrease in gain and heart period range was observed. No difference was obtained in heart rate. Our results demonstrate that the increase of the natriuresis is due, at least in part, to an increase in sodium filtered load.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Kidney/physiology , Pressoreceptors/physiology , Reflex/physiology , Sodium Chloride/administration & dosage , Absorption , Animals , Blood Pressure/drug effects , Diuresis/drug effects , Glomerular Filtration Rate , Heart Rate , Injections, Intraventricular , Kidney/drug effects , Kidney Tubules/metabolism , Male , Natriuresis/drug effects , Pressoreceptors/drug effects , Rats , Reflex/drug effects , Sodium/metabolismABSTRACT
The aim of the investigation was to evaluate the effects of the intracerebroventricular (ICV) injection of 0.1 ml of 1 M NaCl, on the body water distribution in nephrectomized male rats. In comparison with the control rats injected with an equal volume of isotonic saline, the ICV injection of 1 M NaCl elicited 90 min later a significant increase of plasma volume whereas the total water, the inulin space, the calculated interstitial space and the intracellular water were not altered. The increase of plasma volume could be explained by a decrease of capillary efflux to the interstitial space. These results suggest that the ICV injection of 1 M NaCl releases a substance which could regulate the plasma volume.
Subject(s)
Atrial Natriuretic Factor/pharmacology , Body Water/metabolism , Sodium Chloride/administration & dosage , Animals , Injections, Intraventricular , Male , Rats , Rats, Inbred StrainsSubject(s)
Hypertension/epidemiology , Adolescent , Age Factors , Blood Pressure Determination , Child , Female , Humans , Hypertension/diagnosis , Hypertension/prevention & control , Italy , Male , Obesity/diagnosis , Posture , Sex Factors , Skinfold ThicknessABSTRACT
In the rat, the effects of an atrial natriuretic factor (ANF) (Rat, 8-33 Peninsula Lab) on body water distribution have been evaluated. The ANF administration to nephrectomized animals produced a decrease in plasma volume and a slight increase in haematocrit and in plasma albumin concentration. No modifications were observed in total and intracellular water. The fluid efflux from the capillaries appeared to be located in the interstitial space. These results suggest that ANF could regulate plasma volume and systemic blood pressure, concurrently with its other known effects.
Subject(s)
Atrial Natriuretic Factor/physiology , Body Water/physiology , Water-Electrolyte Balance , Animals , Blood Pressure , Blood Volume , Extracellular Space/physiology , Hematocrit , Male , Nephrectomy , RatsABSTRACT
To assess the type and degree of cardiovascular involvement in the early phases of hypertension, 46 adolescents with casual blood pressure (BP) greater than the 95th percentile for age and sex (23 males and 23 females, mean age 14 years) were studied by M-mode echocardiography. Twenty-seven adolescents with casual BP about the 50th percentile, 17 males and 10 females, matched for age, were studied as controls. Adolescents with casual high BP values showed an increase in left ventricular mass (P less than 0.01) and wall thickness to radius (h:R) ratio (P less than 0.01) in comparison to controls. Cardiac index was increased and was correlated with left ventricular mass in hypertensive subjects (P less than 0.05). The correlation between cardiac output and left ventricular mass suggests that cardiac output is a factor in the development of left ventricular hypertrophy.
