Distribution of peptidase activity in teleost and rat tissues

Peptides play important roles in cell regulation and signaling in many tissues. The actions of peptides are regulated by peptidases. Although the activity of these enzymes has been thoroughly characterized in mammals, little is known about their presence or function in fish. In the present study, we compared the activity of several peptidases in selected tissues (pituitary gland, different brain areas, kidney and gills) of the gilthead sea bream and rainbow trout with that found in similar rat tissues (lungs studied in place of gills). Soluble puromycin-sensitive aminopeptidase showed the highest values in the pituitary gland of the sea bream, whereas the membrane-bound form was found to be more active in the trout kidney. Very high levels of activity of aminopeptidase N were detected in trout and sea bream plasma. In contrast, the highest levels of activity of aminopeptidase B were found in rat tissues, with the exception of the gills of the trout. Aminopeptidase N levels tended to be higher in sea bream tissues with respect to those of trout. In contrast, the level of activity of aminopeptidase B was found to be consistently much higher in trout tissues than in those of the sea bream. Prolyl endopeptidase activity was principally detected in the pituitary gland and in the brain areas of teleosts. These differences between species could be related to different mechanisms of osmoregulation in saltwater- and in freshwater-adapted fish.     

Antidiuretic action of prolactin in the rat with diabetes insipidus.

Rats with hereditary hypothalamic diabetes insipidus, devoid of endogenous ADH, exhibited a prompt antidiuresis when injected subcutaneously or intraarterially with ovine prolactin. The antidiuresis was accompanied by a decrease in free water clearance and an increase in urine osmolality without a change in osmolal clearance or creatinine excretion. Measurement of PAH and insulin clearances indicated that prolactin had no effect on renal plasma flow or glomerular filtration rate. Prolactin injection caused a transient decrease in urinary sodium excretion, but proximal tubular sodium reabsorption, estimated by lissamine green transit time, was unaffected. The antidiuretic effect of prolactin could not be attributed to ADH contamination of the ovine prolactin preparation. Kidney cyclic AMP content was increased significantly 5 min after injection of prolactin. Thus, prolactin has an antidiuretic effect similar to that which occurs as a result of ADH action on the kidney and does not require either the release or the presence of ADH in order to cause the antidiuresis. Further, the impaired water excretion cannot be attributed to an increase in proximal tubular sodium reabsorption or to alteration of renal hemodynamics. It is suggested that prolactin has a direct ADH-like action on the kidney resulting in antidiuresis.     

Tyrosinase-like activity and estradiol binding in rat uterine nuclear extracts.

Nuclear extracts from the uteri of estradiol-implanted rats contain a tyrosinase-like enzyme that has three activities: monophenolase or cresolase, diphenolase or catecholase, and estrogen binding. When [3H]estradiol was used as a substrate, 3H2O was released from the A ring in the presence of copper and ascorbic acid. The optimal concentrations of these cofactors for the cresolase activity were established. The cresolase activity was lost on attempts at further purification. Estradiol binding was observed in conjunction with the enzymatic activity and was dependent on the presence of ascorbic acid and copper. The most potent inhibitors of 3H2O release from [3H]estradiol were those with a dihydroxyphenol moiety. The reaction was also sensitive to sulfhydryl reagents. These features of the enzyme are distinctive from other oxidases capable of attacking the aromatic ring of estrogens.     

UMP synthase activity of rat tissue extracts in the bone marrow form of radiation sickness

Whole-body gamma-irradiation of rats with a dose inducing bone marrow radiation syndrome caused phase organospecific changes in UMP-synthase activity. Disturbances of enzymic activity in the bone marrow and spleen well correlated with the dynamics of interphase and reproductive cell death. In brain extracts, UMP biosynthesis from orotic acid did not undergo essential changes.     

Properties of a growth factor activity present in crude extracts of rat uterus

We have shown previously (D.A. Sirbasku, 1978, Proc. Natl. Acad. Sci. U.S.A., 75:3786–3790) that an estrogen-inducible growth factor activity for rat mammary and rat pituitary tumor cells can be identified in extracts of rat uteri, although at the time of that report only a limited biochemical characterization of the activity was presented. In this report, we have evaluated the growth factor activity for lipid, steroid hormone or protein-like properties. Uterine growth factor activity was assayed by measure of the increased cell number of the MTW9/PL rat mammary tumor cell line established by this laboratory and described previously (D.A. Sirbasku, 1978, Cancer Res. 38:1154–1165). Studies showed the following characteristics of growth factor activity: destroyed by trypsin treatment; labile when heated at 80°C; partially denatured by 6 M guanidine or 8 M urea treatment or 50% aqueous solutions of organic solvents; inactivated by extremes of pH or overnight treatment with mild acid; not dialyzable at neutral pH; of apparent molecular weight of 70,000 daltons by G-100 Sephadex chromatography; possessing an isoelectric point of 4.8 to 5.2; not chloroform/methanol extractable; and not in any way identified as either a lipid or a steroid hormone. The data available suggest that the uterine growth factor activity is a protein or polypeptide of apparent high molecular weight, and that this activity does not directly correspond to other known growth factors.     

Influence of phospholipids on the activity of phosphate-dependent glutaminase in extracts of rat liver mitochondria.

Liver glutaminase can be solubilized from frozen-and-thawed mitochondria by treatment with phospholipase A2. Solubilization by this technique markedly changes the kinetic properties of the enzyme. The properties of the membrane-bound form of the enzyme are partially restored by adding phosphatidylcholine or phosphatidylethanolamine to the phospholipase extract. It is concluded that the kinetic properties of liver glutaminase are a function of the interaction of this enzyme with membrane phospholipids.     

Carbohydrase activity in the digestive system of some teleost fishes.

The activity of carbohydrases in Puntius sophore (Ham.), Channa gachua (Ham.) and Cirrhinus mrigala (Ham.) has been studied. The carbohydrases have been found in the stomach, intestinal bulb, intestine, pyloric caeca and the hepato-pancreas. The hepatopancreas is the main site of production of these enzymes and it is in this organ and the intestine that their activity is highest. Their pH optimum lies between 5.4 and 6.4. The enzyme equipment in the teleost is adapted to their respective food and feeding habits both qualitatively and quantitatively. In Puntius (omnivorous) and Cirrhinus (herbivorous) all three carbohydrases, namely amylase (EC 3.2.1.1.), sucrase (EC 3.2.1.26.) and raffinase, while in Channa (carnivorous) only amylase and sucrase have been found to be active. In Cirrhinus mrigala, which is predominantly a herbivorous species, the concentration of carbohydrases is higher than those in the other two fishes.     

Antidiuretic activity of aqueous bark extract of Sri Lankan Ficus racemosa in rats

The decoction (D) of the bark of Ficus racemosa Linn (Family: Moraceae) is claimed as an antidiuretic by some Sri Lankan traditional practitioners. However, the validity of this claim has not been scientifically proven or refuted. The aim of this study was to evaluate the antidiuretic potential of D of the bark of F. racemosa (made as specified in traditional use) in rats using three doses (250, 500 or 1000 mg/kg) following oral administration. The reference drug used was ADH. The results demonstrated both the low- and high-doses of D and ADH significantly impaired the total urine output. The D-induced antidiuresis had a rapid onset (within 1 h), peaked at 3 h and lasted throughout the study period (5 h). However, antidiuretic potential of D was about 50% lower than that of ADH. The D was well tolerated even with subchronic administration. The D caused a reduction in urinary Na+ level and Na+/K+ ratio, and an increase in urinary osmolarity indicating multiple mechanisms of action. The results provide scientific support for its claimed antidiuretic action and deserve intensive scrutiny.     

Effect of splenin and splenic protein-free extracts on the adenosine deaminase activity in various organs of the rat

It has been shown that the adenosine deaminase activity of intact rats increases in such lymphoid organs as the thymus and spleen under the influence of splenic protein-free extracts dissolved in the ratio of 1:100. The enzyme activity in testes does not change but its decrease (by 26.2%) is observed in the adrenal glands under the influence of the splenic protein-free extract. An analogous effect is revealed in splenin and its fractions. The splenic protein-free extract increases (by 83%) the enzyme activity in the thymus of splenectomized rats as compared to intact animals but does not change it in a homogenate of testes.     

Diel activity of littoral and epipelagic teleost fishes in the Mediterranean Sea

Reviews in Fish Biology and Fisheries - Diel activity patterns are an important aspect of behavioural ecology, yet summarising works on diel activity patterns of fishes are lacking for several...