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V Zbuzek

Publications and source records attributed to V Zbuzek.

8 recordsLinked to original sources
PubMed1991

Age-related differences in concomitant hormone release from the superfused rat adenopituitary.

We screened the concomitant release of five adenopituitary (AP) hormones, in vitro, at basal and stimulated conditions, in young and aged (2-3 and 25 months old, respectively) male Fischer 344 rats. The APs of aged rats exhibited significantly higher basal and total release of prolactin, but lower release of luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone and growth hormone than those of young rats. The APs of aged rats did not respond to high K+ depolarization by an increased release of any of the studied hormones, whereas the APs of young rats did release a significant amount in all instances. The results indicate marked age-related alterations affecting the release of the hormones, detectable even in the isolated AP alone.

Aging↗
PubMed1988

Neurohypophyseal aging: differential changes in oxytocin and vasopressin release, studied in Fischer 344 and Sprague-Dawley rats.

We had previously shown that the hypothalamo-neurohypophyseal vasopressin secreting system is suppressed in aged rats. In the present study, using aged (26 months) male Fischer 344 (F344) rats, we showed that in contrast to vasopressin, oxytocin plasma concentration and hypothalamic content were unaltered in comparison with young (2-3 months) rats; however, based on data from our past and current studies, the neurohypophyseal concentrations of both hormones were found to be decreased in aged rats. We also compared the effect of aging on the oxytocin and vasopressin in secretory functions. Superfusion technique was employed to examine oxytocin and vasopressin release from isolated neural lobes of young (2-3 months) and old (26 months) male F344 and young (2-3 months), middle-aged (12 months) and old (30 months) Sprague-Dawley (SD) rats. Aging affected basal release of oxytocin and vasopressin in a differential manner. Expressed per gland, basal release of oxytocin increased in aged rats of both strains; whereas vasopressin release decreased in SD, and did not change in F344, old rats. The vasopressin responses to electrical stimulation, 56 mM K+ and initial traumatic release were decreased in aged rats; whereas oxytocin responses were either unaltered or decreased much less. All age-related changes were more pronounced in SD than in F344 rats. Thus, while the aging process is associated with a significant impairment in the vasopressin secretory function, the oxytocin secretory function is much less affected by that process. Significant strain differences were observed in the effects of aging on oxytocin and vasopressin release.

Aging↗
PubMed1987

Age-related differences in the incorporation of 3H-arginine into vasopressin in Fischer 344 rats.

We studied the effect of aging on the incorporation of 3H-arginine into vasopressin (VP) molecule in the hypothalamus (HT) and the rate of its transport into the neurohypophysis (NH) of male Fischer 344 rats of different ages: 2-3 months (young, n = 28), 11-13 months (adult, n = 30) and 30 months (old, n = 27). 3H-arginine was injected in a single dose through a permanent cannula into the lateral ventricle of an awake animal. The rats were decapitated 1, 6, and 24 h after the injection. VP was extracted from individual HTs and NHs (without pars intermedia), purified in a chromatography column and determined by RIA. Hypothalamus: One hour after the injection the 3H-activity was highest in the young, lower in the adult and lowest in the old rats, whereas the specific activity (cpm/pg VP) was similar in all age groups, reflecting endogenous VP content to be highest in the young, lower in the adult and lowest in the old rats. In the young rats both activities decreased 6 and 24 h after the injection. The adult rats also exhibited declining activities, whereas in the old rats the activities remained unchanged from 1 to 24 h after the injection. Neurohypophysis: One hour after the injection of radioactive label 3H-activity and specific activity were significantly lower in the NH of the old than in those of young and adult rats. The activities increased 6 h after the injection in all age groups with the lowest values in the old rats. After 6 h, both activities in the old rats reached only the 1-h values of the young and adult rats suggesting a delay of at least 6 h in the axonal transport of newly synthetized VP in aged rats. Twenty-four hours after the injection both activities increased in all age groups exhibiting no difference among the age groups, indicating a decreased release of the newly synthetized VP from the NH of aged rats. These data demonstrate an age-related decrease in the rate of incorporation of 3H-arginine into VP, in the rate of its axonal transport and in the release of newly synthetized VP from the NH of Fischer 344 rats.

Aging↗
PubMed1986

Decremental vasopressin release after repeated stimulation of superfused neurohypophyses of Fisher 344 rats of different ages.

We studied the effect of aging on the decline in vasopressin (VP) release from the rat neurohypophyses (NH) as evoked by repeated stimuli with high K+ (56 mM) Locke's solution in vitro. Isolated NHs, without pars intermedia, of 2-, 12- and 30-month-old male Fisher 344 rats arbitrarily labeled as young, adult, and old were individually superfused with synthetic medium TC 199. Following the initial traumatic release, the glands were stimulated three times for 10 min each with recovery periods of 35 min between stimulations. VP was measured by radioimmunoassay. Expressed per mg NH, basal VP release in the old rats, and stimulated VP release in both the adult and old rats, was decreased. The gradual decline (slope) of VP release following subsequent stimuli with high K+ was proportional, however, in all age groups. Thus, decreasing response of VP release to repeated stimulation is a function of the initial response but is not age related. These findings suggest that only some components of the chain of events involved in the release mechanisms are impaired in aging animals, whereas others may remain unaffected.

Age Factors↗