Exploring the Interactive Role of Parathyroid Hormone and Sodium Intake in Inducing Cardiac Hypertrophy in Rats: A Novel Study

Abstract

Background and objectives Previous research has suggested that hyperparathyroidism and excessive salt intake may contribute to the development of cardiac hypertrophy. This study aimed to investigate the relationship and underlying mechanisms between parathyroid hormone (PTH) and salt intake in the development of left ventricular hypertrophy (LVH). Additionally, the study sought to determine whether captopril intervention could reduce the impact of sustained PTH stimulation and excessive salt intake on LVH. Methodology We employed 40 eight-week-old male Sprague-Dawley rats, which were randomly assigned to eight groups: a sham group, a PTH group, a low-salt group (0.6% NaCl), a high-salt group (8% NaCl), a PTH + low-salt group, a PTH + high-salt group, a PTH + low salt + captopril group, and a PTH + high salt + captopril group. The rats were continuously infused with recombinant PTH (1-34) (2 pmol/kg per hour) via an osmotic pump for two weeks and were administered varying concentrations of saline for gavage over two weeks, according to their group. We monitored changes in blood pressure, measured heart weight, left ventricular wall thickness, and myocardial histological morphology, and assessed the relative expression of type III collagen. Results The PTH + high-salt group displayed a significant increase in blood pressure, heart weight, and left ventricular posterior wall thickness (P＜0.05), in addition to myocardial cell hypertrophy and increased Col III expression (P＜0.05), compared to other groups. Captopril intervention significantly reduced blood pressure (P＜0.05), ameliorated myocardial tissue morphology changes, and significantly decreased Col III expression (P＜0.05) but did not entirely reverse the increase in heart weight and left ventricular posterior wall thickness (P＞0.05). Conclusions Our findings suggest that the co-intervention of PTH and high salt can lead to an increase in blood pressure, heart weight, myocardial cell hypertrophy, LVH, and myocardial fibrosis levels in Sprague-Dawley rats. Captopril intervention can lower blood pressure and alleviate pathological myocardial tissue changes and myocardial fibrosis but cannot completely reverse LVH.

Keywords: left ventricular hypertrophy; myocardial fibrosis; parathyroid hormone; renin-angiotensin-aldosterone system; salt.

Figure 1. Influence of parathyroid hormone and different salt intake on rat myocardial tissue morphology (magnification ×400)

(A) Sham group; (B) PTH group; (C) low-salt group; (D) high-salt group; (E) PTH + low-salt group; (F) PTH + high-salt group; (G) PTH + low salt + captopril group; and (H) PTH + high salt + captopril group. PTH, parathyroid hormone

Figure 2. Influence of parathyroid hormone and different salt intake on the expression of type III collagen protein, a marker of myocardial fibrosis (magnification ×400).

(A) Sham group; (B) PTH group; (C) low-salt group; (D) high-salt group; (E) PTH + low-salt group; (F) PTH + high-salt group; (G) PTH + low salt + captopril group; (H) PTH + high salt + captopril group. PTH, parathyroid hormone

Figure 3. Influence of parathyroid hormone and different salt intake on the expression of myocardial fibrosis marker type III collagen protein.

Compared with the sham group: ^*P < 0.05. Compared with the PTH + low-salt group: ^#P < 0.05. Compared with the PTH + high-salt group: ^△P < 0.05. PTH, parathyroid hormone