Structure of Rhythms of Blood Pressure, Heart Rate, Excretion of Electrolytes, and Secretion of Melatonin in Normotensive and Spontaneously Hypertensive Rats Maintained under Conditions of Prolonged Daylight Duration

We studied the structure of rhythms of BP, HR (by telemetric monitoring), electrolyte excretion (by capillary electrophoresis), and products of epiphyseal melatonin (by the urinary concentration of 6-sulfatoxymelatonin measured by ELISA) in normotensive Wistar-Kyoto rats and spontaneously hypertensive SHR rats maintained at 16/8 h and 20/4 h light-dark regimes. In Wister-Kyoto rats exposed to prolonged daylight, we observed changes in the amplitude, rhythm power (% of rhythm), and range of oscillations of systolic BP; HR mezor decreased. In SHR rats, mezor of HR also decreased, but other parameters of rhythms remained unchanged. Changes in electrolyte excretion were opposite in normo- and hypertensive rats. Under conditions of 20/4 h light-dark regime, daytime melatonin production tended to increase in normotensive rats and significantly increased in SHR rats. At the same time, nighttime melatonin production did not change in both normotensive and hypertensive animals. As the secretion of melatonin has similar features in animals of both lines, we can say that the epiphyseal component of the "biological clock" is not the only component of the functional system that determines the response of the studied rhythms to an increase in the duration of light exposure.

Specific Features of Electrolyte Excretion at the Early Stages of Arterial Hypertension in SHR Rats

Daytime and nighttime systolic and diastolic BP was recorded in 23-week-old SHR and Wistar rats by telemetric monitoring. Urine concentrations of sodium, potassium, and calcium were determined in SHR rats during of light (07.00-19.00 h) and dark hours (19.00-07.00 h) at the age of 18, 19, 20, 21, 22, and 23 week; 23-week-old Wistar rats were used as the control. At early stages of the experiment, urine sodium concentration was elevated in SHR rats both at daytime and at night. Thereafter, this value declined and by 22-23 week was significantly lower than in normotensive Wistar rats, but only during daytime. Daytime potassium concentration significantly surpassed the control level during weeks 18-19 of the experiment, but later, a tendency to a decrease in this parameter was observed. Daytime calcium content in SHR rats did not significantly differ from the control throughout the experiment. At night, this value exceeded the control level by more than 2 times during weeks 18-19, but then returned to the level observed in normotensive animals.

Influence of geomagnetic activity and earth weather changes on heart rate and blood pressure in young and healthy population

There are many references in the literature related to connection between the space weather and the state of human organism. The search of external factors influence on humans is a multi-factor problem and it is well known that humans have a meteo-sensitivity. A direct problem of finding the earth weather conditions, under which the space weather manifests itself most strongly, is discussed in the present work for the first time in the helio-biology. From a formal point of view, this problem requires identification of subset (magnetobiotropic region) in three-dimensional earth's weather parameters such as pressure, temperature, and humidity, corresponding to the days when the human body is the most sensitive to changes in the geomagnetic field variations and when it reacts by statistically significant increase (or decrease) of a particular physiological parameter. This formulation defines the optimization of the problem, and the solution of the latter is not possible without the involvement of powerful metaheuristic methods of searching. Using the algorithm of differential evolution, we prove the existence of magnetobiotropic regions in the earth's weather parameters, which exhibit magneto-sensitivity of systolic, diastolic blood pressure, and heart rate of healthy young subjects for three weather areas (combinations of atmospheric temperature, pressure, and humidity). The maximum value of the correlation confidence for the measurements attributable to the days of the weather conditions that fall into each of three magnetobiotropic areas is an order of 0.006, that is almost 10 times less than the confidence, equal to 0.05, accepted in many helio-biological researches.

Features of the Structure of the Circadian Rhythm of Blood Pressure and Heart Rate under Genetically Determined Hypertension in the Experiment

In SHR rats of different ages (22, 26, 30, 34, and 38 weeks), continuous 24-h telemetric monitoring of BP and HR was performed. The amplitude and power of oscillations of diastolic BP significantly decreased at the later stages of arterial hypertension (38 weeks), which was considered as a poor prognostic marker. We also observed a significant decrease in the mean daytime, nighttime, and maximum HR and mesor on weeks 30 and 34, but not on week 38, which can reflect triggering of the adaptive response followed by its exhaustion.