Parathyroid Hormone and Calcitriol in Hypertension Caused by Dietary Calcium Deficiency in Rats

Abstract

Hypertension caused by calcium deficiency in the diet has been linked with an increase in parathyroid hormone (PTH) and calcitriol levels. We evaluated arterial blood pressure (ABP), PTH, and calcitriol in normotensive Sprague-Dawley rats (SDR) and in spontaneously hypertensive rats (SHR) fed from weaning on a control diet with a normal calcium content (1%) or a low-calcium diet (0.1%). The calcemia was also measured in the rats by colorimetric methods. The low-calcium diet decreased the calcemia in both strains and brought about an increase in the ABP which was significant in adult SDR and particularly noticeable during the early hypertensive phase in SHR. The rats fed on this diet had higher hormonal plasma levels when compared with the corresponding values in rats fed on the control diet. In particular, the SDR fed on the low-calcium diet showed much higher PTH (122.6 ± 31.0 pg/ml, p ≤ 0.05) and calcitriol (458.0 ± 13.1 pg/ml, p ≤ 0.01) values than the SDR fed on the control diet (PTH 31.7 ± 2.80 pg/ml; calcitriol 292.1 ± 17.5 pg/ml). These endocrine alterations could justify the increase in ABP caused by dietary calcium deficiency in normotensive rats. Nevertheless, the results of this study indicate that the modifications of the ABP caused by the low-calcium diet in SHR could not be correlated with significant increases in these hormones.

Vitamin D Status in Cattle with Malignant Catarrhal Fever

“…In the present study, serum 1,25-D concentration was found as significantly increased in the MCF group compared with the con- [18,22]. When plasma calcium is decreased, the parathyroid glands are stimulated to produce PTH.…”

“…When plasma calcium is decreased, the parathyroid glands are stimulated to produce PTH. In turn, increased PTH stimulates the upregulation of enzyme CYP27B1 in the kidney to form 1,25-D. Only when plasma calcium returns the normal levels, serum PTH secretion is depressed, and thus, 1,25-D synthesis is depressed [14,18]. In the present study, although serum 1,25-D was increased, serum PTH levels was not increased, quite the contrary serum PTH was significantly decreased in the MCF group compared with the controls (P<0.05).…”

Changes in arterial blood pressure in hypertensive rats caused by long-term intake of milk fermented by Enterococcus faecalis CECT 5728

“…The administration of Ca is paradoxically associated with a decrease in arterial blood pressure, and different studies carried out by our research group have also demonstrated that Caenriched diets can control hypertension in rats (López-Miranda et al 1998;Civantos et al 1999;Civantos Calzada & Aleixandre de Artiñano, 2003;Civantos & Aleixandre, 2004). Dietary Ca supplements also have beneficial effects in hypertensive patients (for reviews see Pryer et al 1995;Allender et al 1996;Resnick, 1999).…”

Efecto De La Clara De Huevo Tratada Con Pepsina Sobre El Desarrollo De Hipertensión Arterial en Ratas Hipertensas Effect of the Hydrolysate Obtained From Egg White With Pepsin on the Development of Hypertension of Spontaneously Hypertensive Rats Efecto Da Clara De Ovo Tratada Con Pepsina Sobre O Desenrolo De Hipertensión Arterial en Ratas Hipertensas

“…Varios grupos de investigación, y también el nuestro, han observado que antes de que se estabilice la presión arterial de las ratas SHR, existe un período inicial en la vida de estos animales en el que esta variable aumenta progresivamente de forma muy marcada, alcanzando la PAS y la PAD valores estables sólo cuando las ratas tienen al menos 10-11 semanas de vida (López-Miranda et al, 1998;Civantos et al, 1999). Como ya se ha indicado en los resultados, las ratas SHR de los grupos control negativo y testigo (las que bebían agua, y las que bebían la solución de clara de huevo sin hidrolizar, respectivamente) presentaron, en realidad, en nuestro estudio valores de PAS y de PAD estables entre las 10 y las 25 semanas de vida.…”