Brain tissue potassium in normal and potassium depleted rats

Active sodium-potassium transports in skeletal muscles of deoxycorticosterone hypertensive rats

CNS-induced suppressions of active Na+, K+ transport was investigated in both 'tonic' muscles, soleus (SOL), and 'twitch' muscle, extensor digitorum longus (EDL) of deoxycorticosterone acetate (DOCA) hypertensive rats. There was a marked K+ loss and Na+ accumulation in the skeletal and smooth muscles of DOCA hypertensive rats. The cellular K+ loss was in the order of SOL greater than EDL greater than diaphragm greater than intestine greater than aorta. However, liver, kidney and CNS organs such as cerebrum, cerebellum and medulla oblongata were spared from this K+ fall. Sciatic nerve sectioning or cervical transection activated the active Na+, K+ transport in SOL during DOCA hypertension but inhibited further the pump activity in EDL. The application of tetrodotoxin on the sciatic nerve also activated the Na+, K+ transport in SOL but inhibited the transport in EDL. The facilitatory effect of denervation on the pump activity in SOL was abolished by pretreatment with ouabain. Injection of curare had no effect on Na+ and K+ contents in both SOL and EDL. These results indicate that the CNS is involved differently on the neural regulations of the active Na+, K+ transport systems in SOL and EDL of DOCA hypertensive rats.

Hypothalamic regulation of sodium-potassium pump activity in skeletal muscle

The suppression of active Na+-K+ transport in rat skeletal muscle during hypokalemia was counteracted by bilateral electrolytic lesion of the ventromedial hypothalamic nucleus. This reversal effect was unaffected even after pancreatectomy or adrenalectomy. The anomalous electrolyte content in hypokalemic rat muscles was aggravated by lesion of the dorsomedial hypothalamic nucleus and of the anterior hypothalamus. The results indicate that the hypothalamus is involved in the regulation of the Na+-K+ transport system in skeletal muscle during hypokalemia.

The electrogenic Na-pump and spontaneous contraction of the hypokalemic rat duodenum

The effects of the electrogenic Na-pump on spontaneous contraction in the isolated, longitudinal muscle of the duodenum of rats which had been on a potassium-deficient diet for 7 weeks, have been investigated. Intracellular levels of Na+ are increased by this diet. The spontaneous contraction of the duodenal muscle was stopped, transiently, by 0.5 to 120 mM-K+ Krebs solution. The period of decrease of tone and amplitude occurring immediately after adding K+ was shortened when the external K+ concentration ([K]o) was increased from 0.5 to 120 mM. The decrease in tone and amplitude induced by K+ was abolished by exposure of the tissue to 0 mM [K]o, by exposure to a temperature below 14 degrees C, and in the presence of ouabain (3 X 10(-5)-10(-4) M). The spontaneous contraction of 'Na-rich' duodenum in bathing medium containing 15 mM K+ and following inhibition of the electrogenic Na-pump with cooling or ouabain was much the same as in the duodenum from rats fed balanced diets: i.e., increase of contractile tone immediately after adding K+. To activate the Na-pump in 'Na-rich' duodenum, the external K+ could be replaced by Rb+, Cs+, NH4+ and Tl3+. The effectiveness was in the order K+ greater than Rb+ greater than Cs+ greater than NH4+ greater than Tl3+. The possible existence of a neuronal or hormonal inhibitory mechanism affecting the active Na-K transport in rat smooth muscle in situ, under conditions of hypokalemia, is discussed.

Effects of hypothalamic lesions on active sodium-potassium transport in the extensor digitorum longus muscles of hypokalemic rat

The CNS-induced suppression on muscle Na+-K+ pump was studied in "twitch" muscle, extensor digitorum longus (EDL), of hypokalemic rats which were fed a K+ deficient diet for several weeks. Peripheral nerve section or bilateral lesion of the ventromedial hypothalamic nucleus had no effect on the Na+ and K+ contents in EDL of hypokalemic rats. However, lesions of the paraventricular nucleus caused the net Na+ loss and the net K+ uptake in the muscles. Lesions in either the dorsomedial nucleus or anterior hypothalamus also caused significant net K+ uptake but the net Na+ loss was not significant. The results were compared with those of "tonic" muscle, soleus, reported previously.

CNS control of active sodium transport in muscle during progressive hypokalemia in the rat

The degree of plasma hypokalemia was graded with the duration of a potassium deficient diet. The intracellular Na+ and K+ contents ([Na]i and [K]i) of the innervated soleus muscle of hypokalemic rats were determined and plotted as a function of plasma K+ concentration following a potassium deficient diet during 1-8 weeks. The progression of plasma hypokalemia was highly correlated with both [Na]i accumulation and [K]i loss in the muscle. Denervation of muscles in the hypokalemic rat resulted in a rapid activation of the Na-pump in the denervated soleus muscle regardless of the degree of plasma hypokalemia. This pump activation in the denervated muscle was chronically maintained throughout the hypokalemia. Restoration of a normal, K+ containing, diet for 4 days in hypokalemic rats resulted in a complete recovery of normal Na+ and K+ contents in both the innervated muscle and plasma, while the [Na]i and [K]i in the denervated muscle was unaffected. The relationship between the CNS-induced inhibition of the muscle Na-pump and the plasma K+ levels in hypokalemic rats is discussed.

Breathing in the potassium depleted rat: the role of metabolic rate and body temperature

Rats with dietary potassium (K) depletion have an altered breathing pattern compared to age matched control rats. The K depleted rats also have a decreased body weight gain, basal metabolic rate and body temperature. In this study, age matched controls are underfed (UFC) to match for body weight gain and metabolic rate and controls are exposed to different ambient temperatures to alter metabolism and body temperature. Compared to UFC rats with the same body weight and basal metabolic rate the K depleted rats breathe slower and with a larger tidal volume in the basal state and in response to hypercapnia and hypoxia. With heat stress body temperature is increased in K depleted rats as is metabolic rate. While frequency is increased it is still slower than in controls at the same ambient and body temperatures. We conclude that the low metabolic rate and body temperature of K depleted rats is not the cause of the altered breathing pattern. In addition, it is shown that the hypothermia of K depletion is present only at ambient temperatures below the thermoneutral zone and that is is apparently due to an inability of the K depleted rat to increase metabolic heat production with cold stress.