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K Poulsen

Publications and source records attributed to K Poulsen.

At least 145 records · Page 8Linked to original sources
PubMed1980

On the sensitivity of metallothioneins to oxidation during isolation.

It is demonstrated that the distribution of metals among the Sephadex G-75 fractions of rat liver and horse kidney supernatant is altered by exposure to oxidizing conditions. In particular, the metals bound to metallothionein are displaced into high-molecular-weight fractions and, to a lesser extent, into the low-molecular-weight forms, under aerobic conditions. In this process, metallothionein zinc is much more labile than cadmium. An appreciable proportion of the thionein is also found in the high-molecular-weight fractions and can be recovered along with the metals by treatment with mercaptoethanol. This result shows that the distributions obtained aerobically with large cadmium content in the high-molecular-weight fractions are an artefact due to metallothionein oxidation and suggests that 'spillage' of metals such as cadmium may be due in large part to oxidative processes rather than saturation effects. Evidence is presented that disulphide-bond formation occurs as thionein becomes bound in the high-molecular-weight region and that chemical reduction is necessary to restore its normal elution behaviour. Mercaptoethanol added to the homogenates maintains the reducing conditions normally found in the cellular milieu and prevents the oxidation of the metallothionein redistribution of the metals during isolation. Under these conditions the rat liver metallothionein isolated from animals exposed to chronic low concentrations of cadmium in drinking water contains appreciable quantities of copper as well as zinc and contains much of the zinc that is present in horse kidney supernatants. Metallothionein can also be extracted from a 40 000g pellet after sonication of the pellet. Thus careful analytical studies of the sites of cadmium deposition in rat liver indicate that greater than 95% is bound to metallothionein.

Animals↗
PubMed1980

Renin in the uterus of pregnant mice. Immunocytochemical, ultrastructural and biochemical studies.

The distribution and content of renin in the uterus of pregnant mice (12--14 days of gestation) was studied by immunocytochemistry, electron microscopy and radioimmunoassay. The uterine renin concentration at this stage of pregnancy was four-fold higher than that of the nonpregnant uterus but still less than 0.1% of the kidney renin concentration. Renin was localized almost exclusively in the decidual and entodermal epithelial linings of the yolk sac (uterine) cavity near the marginal sections of the placenta. By electron microscopy granular and vesicular structures were observed in the renin containing epithelial cells. Chorioallantoic placenta, myometrium, decidua basalis and the antimesometral parts of the epithelial leafs of the uterine cavity did not contain renin. The specific localization of renin suggests a role in parturition or delivery of the placenta.

Animals↗
PubMed1980

Renin in the uterus of non-pregnant mice. Immunocytochemical, ultrastructural and biochemical studies.

The distribution of renin in the uterus of non-pregnant mice was studied by immunocytochemistry, using the peroxidase-antiperoxidase (PAP) technique, by electron microscopy and biochemical renin estimation. By immunocytochemistry, two separate localizations of renin could be identified, one in the apical region of the endometrial cells, the other in perivascular cells of the myometrium. The renin concentration in the endometrium, as determined cytochemically, and the total renin content of the uterus, as estimated enzymatically, varied with the ovarian cycle, being highest during the oestrus and lowest during the post-oestrus phase. The electronmicroscopic finding of the fluctuations in the granule content of the epithelial cells was in accordance with the immunocytochemical and biochemical data.

Animals↗
PubMed1980

Renin-like immunocytochemical activity in the rat and mouse brain.

Renin-like immunoreactivity could be demonstrated in the nuclei paraventricularis, periventricularis and supraopticus of the hypothalamus and in the cerebellar cortex of rats and mice, with both the peroxidase-antiperoxidase (PAP) and fluorescence techniques. The findings are consistent with the assumption of an endogenous angiotensin-forming system in the brain.

Animals↗
PubMed1979

Renin binding proteins in plasma. Binding of renin to some of the plasma protease inhibitors, to lipoproteins, and to a non-trypsin-binding unidentified plasma protein.

Renin is found in mouse plasma as high molecular weight forms, in addition to the fully active 40 000 dalton form. By using freshly 125 I-labelled 40 000 dalton pure submaxillary mouse renin, no binding to plasma proteins was demonstrable. However, unfolding and refolding of the labelled renin by guanidine facilitated binding to specific mouse and human plasma proteins. By using antibodies against individual human plasma proteins, the specific binding proteins were identified to be the plasma protease inhibitors: alpha2-macroglobulin, inter-alpha-trypsin inhibitor, alpha2-antithrombin. Binding was also demonstrated to alpha1- and beta1-lipoproteins, albumin and to a non trypsin binding unidentified plasma protein. No binding to 56 other tested proteins was demonstrable. It is concluded that the native 40 000 renin does not bind, but that a conformational change of the renin molecule most likely is necessary before binding occurs. It is discussed whether or not inactive or high molecular weight forms of renin in plasma are 40 000 renin bound to plasma protease inhibitors and lipoprotein.

Animals↗
PubMed1979

Renin in the mouse submaxillary gland has a molecular weight of 40,000.

The availability of pure submaximillary renin, its antibody and pure specific immunoreactive Fab fragments of the antirenin molecule were used in an attempt to detect in which form renin is stored in the submaxillary gland. The proteolytic activity of serine-, metallo- and sulfhydryl enzymes during homogenisation was inhibited, but no inactive or high molecular weight form could be detected enzymatically or antigenically after gelfiltration. Nor were they demonstrable in crossed immuno-electrophoresis by using antibodies elicited against pure renin. Furthermore, pepstatin which additionally inhibits acid proteases, including a possible autoactivation of renin, and renin specific Fab fragments, were added, the latter in order to steric hinder proteolytic attack on a possible renin precursor. The renin-Fab complex was purified by precipitation with anti-Fab antibodies. No high molecular weight renin was demonstrable in SDS polyacrylamide gel electrophoresis. The only form of renin demonstrable in the submaxillary gland of mice was the fully active 40,000 dalton form. Its specific enzymatic activity was identical to that of pure submaxillary renin, being 0.4 . 10(-3) Goldblatt unit . ng-1.

Animals↗
PubMed1979

Immunocytochemical localization of renin in mouse kidney.

The distribution of renin in mouse kidney was examined in immunohistochemical studies by using an antiserum against pure mouse submaxillary renin and the peroxidase-antiperoxidase (PAP) technique. At antibody dilutions from 1:10(4) to 1:10(6), renin was found in high concentrations in the epitheloid cells of the vasa afferentia and, in lower concentrations, in the wall of some of the vasa efferentia. Renin was also detected in most of the interlobular arteries. Mesangial cells and Goormaghtigh cells were always free of specific staining. At high antiserum concentrations (i.e., dilutions from 1:10(2) to 1:10(4)) specific reaction product was also observed in the apical part of proximal tubule cells. This staining may represent filtered and pinocytozed renin.

Animals↗
PubMed1979

Renin precursor synthesis and renin-binding proteins in the mouse.

1. The precursor synthesis of renin, the storage form in the kidney and the submaxillary gland, and the molecular nature of the forms in plasma were studied in the mouse. 2. Renin is synthesized as a precursor (pre-prorenin) with a molecular weight of 50,000. 3. Renin is stored in the submaxillary gland and the kidneys as fully active renin with a molecular weight of 40,000. 4. The predominant form of renin in plasma is the active mol. wt. 40,000 form. High-molecular-weight forms of renin (800,000 and 70,000) are also present in plasma. 5. Pure 125I-labelled mol. wt. 40,000 renin binds after a change in the tertiary structure, to the plasma protease inhibitors alpha 2-macroglobulin, inter-alpha-trypsin inhibitor and alpha2-antithrombin. It binds also to lipoprotein and an unidentified plasma protein. No binding was seen to more than 50 other studied plasma proteins. 6. The high-molecular-weight forms of renin in plasma may be complexes of renin with plasma protease inhibitors and lipoprotein.

Animals↗
PubMed1979

Differences in renal and submaxillary renin release after stimulation with isoprenaline and noradrenaline.

It is confirmed that while noradrenaline stimulates release of submaxillary as well as renal renin, isoprenaline only stimulates renal renin release. The effects of these two adrenergic agonists differ in several other ways. The kidneys respond to isoprenaline with a dose dependant renin release. As a contrast the submaxillary glands respond to noradrenaline by no or by non-dose-dependant release. After single doses of the agonists the isoprenaline induced renin release is of short duration, contrasting with a prolonged renin release after injection of noradrenaline. The kidneys are able to respond to repeated doses of both agonists, while the submaxillary glands most often only respond to the first dose. While the effect of noradrenaline is blocked by pretreatment with phenoxybenzamine, this blocker is without effect when given after noradrenaline. The two agonists do not provoke any increase in plasma renin in mice which have been both sialoadenectomized and nephrectomized.

Animals↗
PubMed1979

In mice aggressive behavior provokes vast increase in plasma renin concentration, causing only slight, if any, increase in blood pressure.

In mice aggressive behaviour causes a vast release of renin, which can result in about 600-fold increase in plasma renin concentration, reaching 6 Goldblatt Units, corresponding to 15 microgram renin per ml. This increase is mainly due to release of submaxillary renin, but there is also a significantly increased renal renin release. The degree of renin release is influenced by the duration of the aggression and by previous contact with other mice. Contrasting with the vast increase in plasma renin the blood pressure is normal or only moderately increased. This disproportion is not due to the depletion of renin substrate, caused by the increased renin, as shown by the increased calculated renin activity, as well as by decrease in blood pressure elicited by blockade of the renin system. Nor is the disproportion due to change in the sensitivity of the vessels to angiotensin II, the cause of this lack of tachyphylaxis being unknown. By way of exclusion the lack of pronounced increase in blood pressure can be explained by homeostatic function of the cardiovascular reflexes, which may also account for the fact that the pressor response after injection of pure submaxillary renin is only short, contrasting with a prolonged marked increase in plasma renin concentration.

Aggression↗
PubMed1979

Aggression-provoked renin release from extrarenal and extrasubmaxillary sources in mice.

In submaxillary sialoadenectomized and nephrectomized mice aggressive behaviour provoked 5 to 40-fold increases in plasma renin concentration. The changes in renin concentration with time were different in different groups of confronted mice with only partial correlation between the pattern and the observable degree of fight. The changes were similar in sialoadenectomized mice with untouched kidneys as in sialoadenectomized and nephrectomized, indicating that aggression causes no measurable, if any, renal renin release. Repeated aggression with 2 hourly intervals provoked repeated renin release from extrarenal and extrasubmaxillary sources. The renin concentrations of different organs showed the same mutual relationship as in other mammals, but were about 10-fold higher. Splenectomy was without effect on the aggression-provoked renin release. Antibodies against pure mouse renin neutralized the renin in plasma and organs, which contained only insignificant, if any, pepsin activatable inactive renin. Adrenaline, apomorphine, carbachol and dihydralazine were as isoprenaline and noradrenaline without effect on renin release in sialoadenectomized and nephrectomized mice.

Aggression↗
PubMed1978

Characteristics and conversion of high molecular weight forms of renin in plasma and their incomplete activation by the current acid treatment.

Two distinctly different high molecular weight forms of renin are present in mouse plasma in addition to the well-recognized active 40 000 dalton form. The biggest form has a molecular weight of about 800 000, and is stable in 4 M urea, but can be converted to the active 40 000 dalton form, by storage, exposure to acid and limited proteolysis. The 70 000 dalton form can be activated by acid and limited proteolysis. However, the 70 000 dalton form does not change molecular weight with activation. By measuring renin, not only by its enzymatic activity, but also by the direct radioimmunoassay for the renin molecule, which measures enzymatically active as well as inactive renin, it was found that both forms were activated but neither of them completely. The validity of the currently used term "total" renin as the enzymatic renin activity after acid activation, is, therefore, questionable. The quantitative significance of this must await methods which can ensure complete conversion or activation of the high molecular weight forms of renin in plasma.

Animals↗
PubMed1978

Is high-molecular-weight-renin binding of renin to the protease inhibitors and lipoproteins?

1. Two high-molecular-weight forms of renin (molecular weights 800 000 and 70 000) are present in mouse plasma. 2. The 800 000 form could be activated and converted into the fully active 40 000 form, by acid or limited proteolysis. The 70 000 form was activated without change in molecular weight. 3. In addition to its enzymic activity, renin was measured by a direct radioimmunoassay, which revealed that the current acid treatment of plasma did not activate all the renin present. 4. Renin is stored as fully active 40 000 renin, with a specific enzymic reactivity of 0.4 times 10(-3) GU ng(-1), in the submaxillary gland of mice. 5. Pure 125I-labelled 40 000 submaxillary renin did not bind to plasma proteins. However, by changing the tertiary structure of renin, it was bound to some of the plasma protease inhibitors; alpha2-macroglobulin, inter-alpha-trypsin inhibitor and alpha2-antithrombin. It was also bound to alpha1- and beta1-lipoprotein, albumin and an unidentified plasma protein. No binding was seen to more than 50 other studied plasma proteins.

Animals↗
PubMed1977

A direct radioimmunoassay for plasma renin in mice and its evaluation.

The pioneering work of Cohen, S., Taylor J.M., Murakami, K., Michelakis, A.M. and Inagami, T. ((1972) Biochemistry 11 4286-4293) with isolation of submaxillary renin and the first direct radioimmunoassay for renin subsequently described by Michelakis A.M. Yoshida H., Menzie, J., Murakami, K. and Inagami, T ((1974) Endocrinology 94, 1101-1105) was reinvestigated and confirmed. In addition a detailed evaluation of the assay is described by characterization of the immunoreactivity of the labelled renin and demonstration of immunological identity between plasma renin and purified renin standards. Assay and equilibrium conditions were characterized and optimized and the association constant for the antibodies determined to be of the order of 10(11)1/mol. The validity of the direct assay for renin was further investigated by a comparison with another radioimmunoassay for renin; the antibody trapping method, which measures the enzymatic activity of renin in plasma. The correlation coefficient is high (0.91) but does not exclude that the direct assay measures a hypothetical prorenin in plasma as well.

Animals↗