[Pharmacological study on hydrocortisone 17-butyrate 21-propionate (author's transl)]

A lasting symbiosis: how the Hawaiian bobtail squid finds and keeps its bioluminescent bacterial partner

For more than 30 years, the association between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium Vibrio fischeri has been studied as a model system for understanding the colonization of animal epithelia by symbiotic bacteria. The squid-vibrio light-organ system provides the exquisite resolution only possible with the study of a binary partnership. The impact of this relationship on the partners' biology has been broadly characterized, including their ecology and evolutionary biology as well as the underlying molecular mechanisms of symbiotic dynamics. Much has been learned about the factors that foster initial light-organ colonization, and more recently about the maturation and long-term maintenance of the association. This Review synthesizes the results of recent research on the light-organ association and also describes the development of new horizons for E. scolopes as a model organism that promises to inform biology and biomedicine about the basic nature of host-microorganism interactions.

Enhancement of affinity to receptors in the esterified glucocorticoid, hydrocortisone 17-butyrate 21-propionate (HBP), in the rat liver

To investigate the affinity of glucocorticoid (GC) to its receptor, the binding of [3H]hydrocortisone 17-butyrate 21-propionate ([3H]HBP) and [3H]dexamethasone ([3H]DEX) in rat liver was analyzed kinetically. Scatchard analysis of [3H]hydrocortisone ([3H]HC) binding yielded a curvilinear plot with upward concavity with high and low affinities. The dissociation constant (Kd) value of high affinity was 1.9 nM and of low affinity 68.7 nM. A Scatchard plot of [3H]HBP binding showed a straight line with high affinity. The Kd value was 9.8 nM. The Kd values for the low affinity site of HC were in good agreement with the Ki values obtained from displacement experiments of [3H]DEX and [3H]HBP binding. The Ki values of HC for [3H]DEX and [3H]HBP were 51.9 and 42.3 nM respectively. The association rate constant for HBP to the GC receptor was 2.9 times lower than that for HC. The dissociation rate constant for HBP was 6.1 to 8.3 times lower than that for HC. The Kd values for [3H]HBP (9.5 nM) and [3H]HC (30.0 nM) obtained from the above two rate constants were approximately the same as the Ki and Kd values (in the case of HC, the value of the low affinity site). These results suggest that esterification of the hydroxyl group(s) in the side chain of GC by butyrate and propionate increased the affinity to the GC receptor, and that a decrease in the dissociation rate from the receptor caused the increase in the affinity to the GC receptor.

Characteristics of binding of a new anti-inflammatory glucocorticoid, hydrocortisone 17-butyrate 21-propionate (HBP), to glucocorticoid receptors of rat liver

Characteristics of the specific binding of hydrocortisone 17-butyrate 21-propionate (HBP) to the cytoplasmic fraction from rat liver were investigated. The inhibition constant (Ki) of HBP for the site of 3H-dexamethasone (3H-DM) binding was approximately equal to the value of DM and significantly smaller than that of hydrocortisone (HC). The maximum number of binding sites (Bmax) and dissociation constant (Kd) for 3H-HBP were also approximately equal to those for 3H-DM. The Scatchard and Hofstee plots analyses of 3H-HC binding indicated that the HC binding sites consisted of three components with different affinity, while that of 3H-DM had only one site with an intermediate affinity. HBP and hydrocortisone 17-butyrate (HB) bound to other binding sites of HC in addition to the site for DM. The IC50 value for synthetic glucocorticoids determined from the inhibition curves of 3H-HC binding in the first phase agreed with the values determined by the displacement study of 3H-DM binding. Furthermore, the first phase of HBP in the inhibition curve of 3H-HC binding disappeared from the curve, and only the second phase remained following the addition of DM. These results indicate that the esterification of C-17 and C-21 OH increases the affinity of the binding site for synthetic glucocorticoid and attenuates the affinity for the other binding sites of HC.