Percutaneous absorption of steroids: Determination of in vitro permeability and tissue reservoir characteristics in human skin layers

The skin localization of steroids following topical application is largely unknown. We determined the distribution of five steroids in human skin using excised epidermal, dermal, and full-thickness membranes in vitro. There was no significant difference in steroid maximum flux through epidermal and full-thickness membranes, other than significantly lower fluxes for the most polar steroid, aldosterone. Hydrocortisone had the highest dermal diffusivity and dermal penetration, and the accumulation of hydrocortisone and corticosterone was higher than that of the other steroids. Slower penetration and higher accumulation in the viable epidermis of progesterone in full-thickness skin were consistent with dermal penetration limitation effects associated with high lipophilicity. Copyright (c) 2006 S. Karger AG, Basel

Cloning and characterization of natriuretic peptides from the venom glands of Australian elapids

The venom from Australian elapid snakes contains a complex mixture of polypeptide toxins that adversely affect multiple homeostatic systems within their prey in a highly specific and targeted manner. Included in these toxin families are the recently described venom natriuretic peptides, which display similar structure and vasoactive functions to mammalian natriuretic peptides. This paper describes the identification and detailed comparative analysis of the cDNA transcripts coding for the mature natriuretic peptide from a total of nine Australian elapid snake species. Multiple isoforms were identified in a number of species and represent the first description of a natriuretic peptide from the venom gland for most of these snakes. Two distinct natriuretic peptide isoforms were selected from the common brown snake (Pseudonaja textilis), PtNP-a, and the mulga (Pseudechis australis), PaNP-c, for recombinant protein expression and functional analysis. Only one of these peptides, PtNP-a, displayed cGMP stimulation indicative of normal natriuretic peptide activity. Interestingly, both recombinant peptides demonstrated a dose-dependent inhibition of angiotensin converting enzyme (ACE) activity, which is predictive of the vasoactive effects of the toxin. The natriuretic peptides, however, did not possess any coagulopathic activity, nor did they inhibit or potentiate thrombin, adenosine diphosphate or arachidonic acid induced platelet aggregation. The data presented in this study represent a significant resource for understanding the role of various natriuretic peptides isoforms during the envenomation process by Australian elapid snakes. (c) 2006 Published by Elsevier Masson SAS.

Further evidence of linkage at 7p22 with familial hyperaldosteronism type II

Primary aldosteronism (PAL) is caused by the autonomous over-production of aldosterone. Once thought rare, it is now reported to be responsible for 5–10% of hypertension. Familial hyperaldosteronism type II (FH-II), unlike familial hyperaldosteronism type I, is not glucocorticoid-remediable and not associated with the hybrid CYP11B1/CYP11B2 gene mutation. At least five times more common than FH-I, FH-II is clinically, biochemically and morphologically indistinguishable from apparently sporadic PAL, suggesting that its incidence maybe even higher. Studies performed in collaboration with C Stratakis (NIH, Bethesda) on our largest Australian FH-II family (eight affected members) demonstrated linkage at chromosome 7p22. Similar linkage at this region was also found in a South American FH-II family (DNA provided by MI New, Presbyterian Hospital, New York). Mutations in the exons and intron/exon boundaries of the PRKARIB gene (which resides at 7p22 and is closely related to PRKARIA gene mutated in Carney complex) have been excluded in our largest Australian FH-II family. Using more finely spaced markers, we have confirmed linkage at 7p22 in these 2 families, and identified a second Australian family with evidence of linkage at this locus. The combined multipoint LOD score for these 3 families is 4.87 (θ=0) with markers D7S462 and D7S2424, which exceeds the critical threshold for genome-wide significance suggested by Lander and Kruglyak (1995), providing strong support for this locus harbouring mutations responsible for FH-II. A newly identified recombination event in our largest Australian family has narrowed the region of linkage by 1.8 Mb, permitting exclusion of approximately half the genes residing in the original reported 5Mb linked locus. In addition, we have strongly excluded linkage to these key markers in two Australian families (maximum multipoint LOD scores −3.51 and −2.77), supporting the notion that FH-II may be genetically heterogeneous. In order to identify candidate genes at 7p22, more closely spaced markers will be used to refine the locus, as well as single nucleotide polymorphism analysis.