Serum Inorganic Phosphate and Alkaline Phosphatase Activity in Cold-Exposed Rat

To characterize serum constituents in blood in response to cold exposure, we measured serum inorganic phosphate (Pi) and alkaline phosphatase (ALP) levels. After 30 min exposure of cold, the serum Pi and alkaline phosphatase levels were 3.4 ± 0.06 mg/l and 72.33 ± 0.45 μmole/l respectively where as the control levels of these constituents are 3.05 ± 0.03 mg/l and 84 μmole/l respectively. Cold exposure for 30 min induces serum Pi concentration by 11.5 % and decreases ALP levels significantly by 13.9 % compared to control rats. Serum Pi for 1 h and 2 h were 3.8 mg/l and 4.17 ± 0.16 mg/l while ALP levels were 57.33 ± 0.88 μmole/l and 91 ± 1.73 μmole/l respectively in different groups of rats. Cold exposure stimulates serum Pi by 24.6 % and 36.7 % and reduces ALP activity by 31.7 % significantly and without significant change for 1 h and 2 h respectively. Another groups of rats exposed to cold for 4 h had Pi and ALP levels 4.66 ± 0.88 mg/l and 85.66 ± 0.88 μmole/l respectively. Cold exposure similarly stimulates Pi content significantly by 52.8 % without affecting ALP activity compared to the control rather reaches to basal level. Our results demonstrate that Pi and ALP levels in cold-exposed rats are regulated in different ways. TAJ 2006; 19(1): 13-17 1 Associate Professor, Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi-6205. 2 Associate Professor, Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi-6205. Introduction Homeostasis of living organism is an important feature. The changes in environmental factor affect the homeostasis of the living cell. However, the organism has the capability to maintain this homeostasis. Cold exposure is the major sympathetic stimuli disrupts the homeostasis of serum constituents. After prolonged exposure of rats to cold, a sustained increase in systolic pressure occurs, giving rise to a cold-induced model of hypertension . Activation of the sympathetic nervous system is thought to contribute to the development of hypertension in cold-exposed rats. Serum inorganic phosphate and alkaline phosphatase (ALP) are important constituent in blood. However, the regulatory mechanism of the molecules in blood is not clearly understood. Serum Pi and ALP are the tools for the proper diagnosis of disease. In the pathological condition, these constituents are changed. The degradation of cellular ATP is a common phenomena either by the environmental stress or by endogenously through hydrolytic enzyme. As a result, the serum Pi is increased. ALP levels are also increased in the pathological condition preferentially in liver disease, kidney disease etc. However, very little is known whether the cold exposure can influence the concentration of these molecules in the serum. Therefore, we examine the effect of cold stress on the Pi and ALP levels in rats. Materials and Methods Animals: Male rats weighing 200 to 260 g were used. They were housed in the cages at ambient temperature and given free access to laboratory foods and water. In the day of experiment, cold exposure (4-8C) were given to the different groups of rats in the cold chamber for 30 min, 1 h, 2 h and 4 h with full aeration and with free access of water. After cold exposure treatment, the rats were immediately anesthetized with diethyl ether and were quickly decapitated. Blood was drawn from the jugular vein and was centrifuged at 3000 rpm for 10 min. The serum in the supernatant was kept at –20C. Estimation of serum inorganic phosphate (Pi) and activity of alkaline phosphatase (ALP) : Serum Pi was estimated by calorimetric method and ALP was estimated according to the prescribed procedure. All data, expressed as means ± SE, were analyzed using analysis of variance (pared ttest) by Stat View soft ware.