摘要:

The hepatic clearances of somatostatin (SS)-28 and SS-14 by the perfused rat liver were compared, using a recirculating, plasma-free, erythrocyte-containing perfusion system. The disappearance rate constant, half time, clearance, and hepatic extraction ratio when 1.2 nM SS-28 was added to the perfusate were 0.0221 ± 0.0051 min−1, 36.6 ± 7.6 min, 0.34 ± 0.08 mL/min, and 17.2 ± 3.9%, respectively. The corresponding values obtained when SS-14 was added to the perfusate were 0.0405 ± 0.0022 min−1, 17.3 ± 1.0 min, 0.71 ± 0.05 mL/min, and 35.4 ± 2.6%, respectively. The differences between the SS-28 and SS-14 indices were all statistically significant. In addition, the perfusates with SS-28 added were eluted on Sephadex G-25 fine columns and somatostatinlike immunoreactivity (SLI) was determined. No SS-14 was found in perfusate containing SS-28 at both 5 and 30 min after the beginning of the perfusion. To investigate whether or not the liver plays an important role in the clearance of SS-28 or the conversion of SS-28 to SS-14in vivo, the plasma disappearance of 2 μg SS-28 was compared in the whole rat and the functionally hepatectomized model. The half time of plasma SS-28 was 1.43 ± 0.12 min in the whole rat, significantly shorter than the 2.20 ± 0.14 min in the hepatectomized model. Gel filtration of plasma extract samples at 0.5 min after the SS-28 injection showed two major peaks of SLI: a first peak corresponding to SS-28 and a second peak coeluted in the position of SS-14 in both the whole rat and the hepatectomized model. At 4 min after the SS-28 injection, the first peak disappeared and only a small second peak was observed. These results suggest that SS-28 is cleared by the rat liverin vivoandin vitroand that it is cleared more slowly than SS-14. Furthermore, we find that little, if any, conversion of SS-28 to SS-14 occurs in the liver.

ISSN:0008-4212    

DOI:10.1139/y85-011

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

To determine the role of the nutritional state in nonshivering thermogenesis during cold adaptation, cold adaptability was compared between cold-adapted (5 °C for 4–5 weeks) rats fedad libitumand cold-adapted rats pair fed with warm controls having the same food intake. Cold-adapted pair-fed rats suffered a significant loss in body weight during cold exposure. However, brown adipose tissue (BAT) in both cold-adaptedad libitumfed and cold-adapted pair-fed rats was enlarged to the same extent as compared with that in control rats. Fat-free dry matter in BAT also increased in cold-adaptedad libitumfed and cold-adapted pair-fed rats to the same extent. Cold tolerance as assessed by the change in the colonic temperature at −5 °C was improved relative to control rats and was the same for cold-adaptedad libitumfed and cold-adapted pair-fed rats. Nonshivering thermogenesis as estimated by the noradrenaline-induced increase in oxygen consumption was significantly greater in the cold-exposed rats and there was no significant difference between cold-adaptedad libitumfed and cold-adapted pair-fed rats. These results suggest that an improved cold tolerance by means of nonshivering thermogenesis in brown adipose tissue is closely related to the low temperature itself but not the increased food intake which occurred in the cold.

ISSN:0008-4212    

DOI:10.1139/y85-012

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The aim of the present study was to investigate the influence of hypoxemia combined with respiratory acidosis on the kinetics of digoxin in conscious dogs. One group of three beagles was exposed to air and 7 days later to 10% O2, 10% CO2, and 80% N2. In a second group of three dogs, the order of exposure to the two atmospheric conditions was reversed. The dogs received 25 μg/kg digoxin and blood and urine samples were collected over the next 29 h. At the conclusion of the second treatment, the dogs were sacrificed to determine digoxin concentrations in the left ventricle, liver, renal cortex, and skeletal muscle. Digoxin total body clearance increased from 6.2 ± 0.9 in control to 9.0 ± 1.0 mL min−1 kg−1in hypoxemic and hypercapnic dogs (p < 0.05). The digoxin apparent volume of distribution at steady state (Vss) was increased in the dogs with hypoxemia and hypercapnia (11.63 ± 1.11 vs. 8.62 ± 0.41 L/kg in the controls,p < 0.05). As a consequence the digoxin plasma half-life remained unchanged (18.6 ± 1.5 h in hypoxemic and hypercapnic dogs versus 20.1 ± 2.8 h in the controls). In dogs with hypoxemia and hypercapnia, the ratio of tissue to plasma digoxin concentrations tended to increase in the liver, in the renal cortex, and in the left ventricle and remained unchanged in the left hind leg muscle.In vitrostudies showed that the digoxin total binding to erythrocyte membranes was slightly increased in the dogs with hypoxemia and hypercapnia, resulting from an increase in the apparent intrinsic association constant for digoxin (p < 0.003). It is concluded that hypoxemia combined with respiratory acidosis changes digoxin disposition in the conscious dog and is the cause of a digoxin redistribution into the tissues.

ISSN:0008-4212    

DOI:10.1139/y85-013

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Enzyme activities related to aerobic metabolism and cyclic nucleotides were evaluated in muscle and nonmuscle cells of rat heart. The perinatal period from weaning to adult was studied. Malate dehydrogenase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase activities of nonmuscle cells equal or exceed muscle cell activities in the weanling heart. Aerobic enzymes remain unchanged in nonmuscle cells during growth; however, muscle cell activities are enhanced. Adenylate cyclase and guanylate cyclase activities are higher in heart homogenates of weanling than adult rats. Despite elevated adenylate cyclase activity, cyclic AMP levels are identical in weanling and adult rats. Cyclic GMP levels are twofold higher in weanling than in adult rats. Muscle cell metabolism and cyclic nucleotide levels are associated with growth-related changes in heart function and cellularity, respectively.

ISSN:0008-4212    

DOI:10.1139/y85-014

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Intracerebroventricular administration of a C-terminal cholecystokinin (CCK) antiserum potentiated the analgesic and cataleptic effects of (β-endorphin. The results are opposite to those observed after injection of CCK-8. It was suggested that CCK-8 may play a physiological role antagonizing the action of β-endorphin.

ISSN:0008-4212    

DOI:10.1139/y85-015

出版商:NRC Research Press    

年代:1985

数据来源: NRC