Changes in hexokinase isoenzymes in regions of rat brain during thyroid deficiency

In this work, activities of hexokinase isoenzymes Type I and Type II were measured in the soluble and particulate fractions from the brain regions (cerebral hemispheres (cerebrum), cerebellum and brain stem) of the thyroidectomized adult rats as well as of the thyroidectomized rats administered with triiodothyronine. Thyroidectomy generally decreased the hexokinase activity associated with particulate and soluble fractions. Hexokinase Type II isoenzyme was more affected than the Type I isoenzyme. Administration of triiodothyronine to the hypothyroid rats abolished the effect of thyroidectomy. Adult brain enzymes have been generally considered not be affected by thyroid hormones. The data obtained in this work are suggestive of an effect of thyroid hormones on hexokinase in the adult brain. Since the effects of thyroidectomy on the energy metabolism of the heart tissue are well known, the heart tissue was also studied for comparison.

Blockade of ovulation by prostaglandins synthesis inhibitor in medial preoptic area

Indomethacin, a known inhibitor of prostaglandins synthesis, injected into the medial preoptic area on the day of proestrus blocked ovulation in regularly cycling female rats. This finding provides evidence for a facilitatory role of endogenous prostaglandin synthesis, in the medial preoptic area, in the process of ovulation.

Metabolic activity of lysosomes in tin-intoxicated regenerating rat liver

The metabolic activity of lysosomes was monitored by assaying the lysosomal enzymes. DNase, RNase, acid phosphatase and cathepsin in rat liver regenerating after partial hepatectomy at various intervals after the operation. Results of the present study demonstrate that the activities of lysosomal enzymes are increased significantly during the process of rapid regeneration, especially at 24 h and 48 h. A small rise in enzymatic activities was noticed at 36 and 72 h of regeneration, leading towards normalisation at 168 h. Administration of tin(II) tartrate (25 mu mol Sn2+/100 gm body wt.) significantly increased the DNAse and RNAse activity at 24 h of the regeneration, while a decrease was noticed in acid phosphatase activity. An increase was also found in the catheptic activity of tin-treated hepatectomized rats. It can thus be concluded that an increased metabolic activity of lysosomes is reflected by the increased activity of its hydrolytic enzymes during the regeneration, and tin at low concentrations is helpful to this process. Further work is in progress to gain insight into the other metabolic activity of the lysosomes during the process of regeneration.

Influence of polyaminocarboxylic acids on the removal of manganese-54 from the body organs of sham-operated and partially hepatectomized rats

EDTA, 1,2-cyclohexylenediamine tetra-acetic acid (CDTA), hexamethylene 1,6-diamine N,N,N',N'-tetra-acetic acid (HDTA), diethylene-triamine pentaacetic acid (DTPA) and nitrilotriacetic acid (NTA) were examined for the removal of manganese-54(54Mn) from some organs of sham-operated and partially hepatectomized rats in early manganese (Mn) poisoning. CDTA was found to be most effective in removing 54Mn from the liver of both sham-operated and hepatectomized rats. These chelating agents also lowered the Mn levels in kidney, spleen and brain of poisoned rats. Although a significantly higher accumulation of Mn was observed in hepatectomized rats, there was no significant difference in the efficiency of the chelating agents in removing Mn from the body organs of poisoned animals of both the sham-operated and hepatectomized groups. An attempt has been made to seek a possible correlation between % removal of Mn by various polyaminocarboxylic acids and their corresponding stability constants.

Changes in hexokinase isoenzymes in regions of rat brain during insulin-induced hypoglycemia

Activities of hexokinase isoenzymes were determined during insulin-induced hypoglycemia in soluble and total particulate fractions from three regions of rat brain. Type I hexokinase isoenzyme activity showed a small decrease in both soluble and particulate fractions from the cerebral hemispheres. In cerebellum and brain stem, however, Type I isoenzyme showed a decrease only in the soluble fraction. A significant increase was observed in hexokinase Type II isoenzyme from both the fractions, in all the three brain regions 1 h after insulin administration.

The effect of cadmium and manganese on the distribution of iron-59 in partially-hepatectomized rats

The distribution of iron-59 in blood at various time intervals was studied in sham and partially-hepatectomized rats after a single intravenous injection of 59Fe (III) citrate. A significant difference was observed in the rate of disappearance and reappearance of iron-59 in circulation. Administration of cadmium and manganese at a concentration of 0.5 and 2 mg/kg b.wt., respectively, did not cause any significant change in this pattern. A significant decrease in iron-59 incorporation in the liver of hepatectomized rat was produced by cadmium while manganese had no effect.

Haem and drug-metabolizing enzymes in regenerating rat liver

Various parameters of haem and drug metabolism were measured during the course of liver regeneration after two-thirds hepatectomy. Partial hepatectomy produced a significant depression in delta-ALA synthetase and delta-ALA dehydratase, and induction in haem oxygenase at an early stage of regeneration. The values returned to normal within 7-14 days. These changes were also accompanied by a marked decline in benzo(a)pyrene hydroxylase and aminopyrene demethylase. The level of glutathione and the activity of glutathione reductase also increased during the early stage of proliferation. The increased level of glutathione with concomitant decrease in drug-metabolizing enzymes and induction in haem oxygenase could be considered as a protective mechanism for the detoxication process, although a contribution from other biotransforming mechanisms cannot be excluded.

Effect of nitrilotriacetic acid (NTA) on the distribution of manganese-54 in rats

The effect of single dose of NTA on the removal of radio-manganese in various organs and in plasma has been studied in rats which received single i.v. injection of 54Mn(II). The lowered value of radio-manganese in NTA treated rats as compared to control animal indicates that NTA binds rapidly and forms stable and diffusible complex resulting in the fast excretion of the injected 54Mn(II).

The effect of metal salts on the distribution of iron-59 in rats: Manganese (II), nickel (II) and tin (II)

The disappearance and reappearance of iron-59 in plasma and blood at various time intervals has been studied in control, manganese, nickel and tin administered and anaemic rats after a single intravenous injection of an aqueous solution of radioactive iron (III) citrate. Significant difference was observed in the rate of reappearance of iron-59 in the circulation between control and manganese treated animals. The disappearance of iron-59 from the plasma of control and treated animals however did not show any appreciable difference. A significant increase in the radio-iron content was observed in bone marrow, liver and kidney of treated animals as compared to control group forty eight hours after Fe-59.

The distribution of manganese-54 in fetal, young and adult rats

The distribution of 54Mn in various organs of pregnant rats and of their 19-day-old fetuses and in non-pregnant female rats of various ages has been studied 18 h after an i.v. injection of 54MnCl2. The results indicate that early neonates are more susceptible to manganese (Mn) than the growing rats. The localization of 54Mn in liver and brain of the embryo was highly significant.