[Blood serum level of primary bile acids in cattle, horses, swine and dogs]. / Blutserumspiegel primärer Gallensäuren bei Rind, Pferd, Schwein und Hund.

The levels of the two primary bile acids, cholic acid (CA) and chenodeoxycholic acid (CDCA), were determined by radioimmunoassay in cattle, horse, pig and dog serum. The mean serum cholic acid (SCA) and deoxycholic acid (SCDCA) levels of cows varied with their reproductive status, being 7.8 (+/- 3.3) and 1.5 (+/- 1.0) mumol/l in dry cows, 17.8 (+/- 6.9) and 2.3 (+/- 1.0) mumol/l in freshly calved dams, and 15.8 (+/- 5.7) and 2.3 (+/- 0.8) mumol/l, respectively, in lactating cows. The SCA level found in the immediate prepartal period and also on the day of calving corresponded to those found during the dry period, then, they tended to rise 2 days after calving and attained the peak characteristic for freshly calved dams on day 3 or 4 post partum. Feed consumption had no influence on the serum levels of primary bile acids, and circadian variations of SCA and SCDCA were also negligible. Suckling calves had much lower SCA levels (2.3 (+/- 1.0) mumol/l before feeding than cows. This initial concentration rose to 10.3 (+/- 2.9) mumol/l 1 h after feeding and returned to 5.0 (+/- 2.1) mumol/l 3 h later. Like cows, horses showed no appreciate difference between pre- and post-feeding levels of SCA (2.2 (+/- 1.2) mumol/l) and SCDCA (1.1 (+/- 0.3) mumol/l). Unlike bovines, pigs and dogs showed a considerable increase in the serum levels of the primary bile acids after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between thyroid hormone level and blood pH in cows and in their offspring.

Thyroid hormone levels in the plasma and blood pH were compared in 38 newborn calves and their dams immediately at parturition, then 24 and 72 h thereafter. Both thyroid hormone levels and pH exhibit much higher variation in calves than in cows. Applying a linear model at different sampling times, a weak (r = -0.112 to -0.397) but significant (P less than 0.05) negative correlation was found between thyroid hormone levels and blood pH in calves 24 and 72 h postpartum. At birth, when no correlation was found with linear approach, a polynomial regression model showed curvilinear relationship between thyroid hormone levels and blood pH in calves. Since these correlations could not be substantiated by comparing data of different sampling times, one can conclude that the possible relationship of thyroid hormone levels and blood pH is a complex one. Revealing the underlying mechanism of the above observations requires further study.

Adaptation of 5'-deiodination to hypothyroid conditions following surgical and/or radiothyroidectomy in chickens.

The effect of thyroidectomy on serum levels of thyroid hormones (thyroxine, T4; triiodothyronine, T3) and on tissue levels of T3 as well as on 5'-deiodination (5'-DI) in liver, kidney and brain of chickens was investigated. The most effective way of thyroidectomy was a combined surgical (Tx) plus radiothyroidectomy (RTx) with low amounts of 131-I (NaI). The latter destroyed extra-thyroidal hormone production. It was found that even if after Tx and RTx the serum levels of T4 and T3 were close to the detection limit, the tissue T3 level was only half of normal in liver and kidney and remained normal in the brain. It is suggested that lowered 5'-deiodination is an important but not exclusive factor contributing to this adaptation of cells to hypothyroid conditions.

Restricted feed intake influences thyroid hormone production and peripheral deiodination in chickens.

Thyroid hormones are of major importance in determining metabolic state both in mammals and in birds. Whether or not feed intake itself has an autoregulatory role in adjusting the setpoint of thyroid hormone activity is yet not well understood. The present work investigates the effects of restricted feed intake on the serum levels and on the peripheral metabolism of thyroid hormones. Also, the sensitivity of the pituitary-thyroid axis was looked at by means of thyrotropin releasing hormone provocation test. Several groups of Hunniahybrid chickens aged 2-6 weeks were used. Restriction was made by providing the experimental animals 70 and 85 percent of the amount of food consumed in the ad libitum fed control group. It was found that feed restriction lowers circulating concentration of triiodothyronine probably by inhibiting the activity of liver deiodinase and also decreases the sensitivity of the pituitary-thyroid axis meaning that both central and peripheral regulatory mechanisms of thyroid economy are affected by feed restriction.

Acute changes of the conversion of thyroxine to triiodothyronine in hypophysectomized and thyroidectomized chickens exposed to mild cold (10 degrees).

The effect of acute cold (10 degrees) exposure on the tissue level of triiodothyronine (T3) and on the conversion of thyroxine (T4) to triiodothyronine, both in vitro and in vivo, has been investigated in young chickens previously thyroidectomized or hypophysectomized. It was found that cold exposure stimulates T4 to T3 conversion both in vivo and in vitro not only in intact animals but also in hypophysectomized and thyroidectomized ones. It is concluded that peripheral metabolism of thyroid hormones represents a self-standing but not sole route of adaptation to changes in environmental temperature.

Thyroxine, triiodothyronine, reverse-triiodothyronine, and other physiological characteristics of periparturient cows fed restricted energy.

Eighty-six cows were assigned to two equal groups with group A fed according to National Research Council recommendations for total digestible nutrients for the 8 wk before parturition and group B was fed 21% higher energy in the first 6 wk and 15% higher in the last 2 preparturient wk. Thyroxine in blood serum decreased in both groups 14 days before and on the day of delivery. It was significantly lower in group A. Findings were similar with triiodothyronine. Blood serum concentrations of reverse-triiodothyronine of group A was significantly higher in group A on day 28 and 14 than group B before delivery. Energy intake had little influence on the serum concentrations of other constituents (albumin, total protein, immunoglobulin G, total and free cholesterol, nonesterified fatty acids). Restricted energy intake that does not alter thyrotropin-thyrotropin-releasing hormone secretion results in higher rate of production of reverse-triiodothyronine and in decreased serum concentration of triiodothyronine. Slight changes of energy balance might be indicated readily by reverse-triiodothyronine concentration in blood serum.

Studies on the conversion of thyroxine to 3,5,3'-triiodothyronine in normal and thyroidectomized chickens.

The possibility of conversion of L-thyroxine (T4) to L-3,5,3'-triiodothyronine (T3) and to 3,3',5'-triiodothyronine (reverse-T3, r-T3) has been investigated in chickens. Reverse-T3 could not be detected in normal animals. Both thyroidectomized and normal animals were able to convert exogenous T4 to T3. The administration of propylthiouracyl blocked this conversion to a greater extent than had been expected from the data on mammals. The conversion ratio is higher than in any other species reported in the literature. Data suggest that, as a result of the adaptation of the peripheral deiodination, thyroidectomized animals were able to convert more T4 to T3 than were normal ones.

Daily fluctuations of peripheral metabolism of corticosterone in male Japanese quails: a dynamic approach to the development of plasma corticosterone daily rhythm.

An ultradian rhythm was found in the daily variation of the parameters concerning the peripheral metabolism of corticosterone in sexually mature male Japanese quails. The period of this rhythm was eight hours; three peaks and minima were found in the daily fluctuation of metabolic clearance rata and an antiphysed rhythm in the biological half-life as well as in tetrahydrocorticosterone/corticosterone conversion rata. The findings emphasize the importance of the peripheral metabolism in developing of corticosterone plasma levels; and analyze the circadian rhythm of corticosterone plasma level as a result of secretion rate and peripheral disappearance.