Highly purified ACTH and MSH peptides were studied in isolated rat glomerulosa and inner zone cells and their activity compared with that in an Anolis melanophore assay. While both ACTH1-39 and ACTH1-24 were almost equally potent steroidogenic peptides in the two cell types (ED50 between 1 and 4 \ m=x\ 10\m=-\12 m), \g=a\-MSHdisplayed only weak steroidogenic activity. Although it was a full agonist, it was about 104-fold less potent in both capsular and inner zone cells. \g=b\-MSH(porcine) was even 10-fold less active in capsular cells than \g=a\-MSH, and in inner zone cells it was a partial agonist. Highly potent melanotropic peptides, such as (Nle4, D-Phe7)-\g=a\-MSH or cyclic (Cys4, Cys10)-\g=a\-MSH were either inactive or exhibited only a very slight partial steroidogenic activity in both cell types. Comparison of the activity profile of additional compounds, such as des-acetyl \g=a\-MSH,(Tyr(I)2)-\g=a\\x=req-\ MSH, ( Tr p( For ) 9) -\ g=a\ -MSH or ( Nva12-\ g=a\ -MSH in the adrenocortical and pigment cell assays led to the conclusion that \ g=a\ -MSH does not exert its steroidogenic effect through a typical melanocyte-type of MSH receptor, but rather through a low affinity-type of ACTH receptor.

Hematopoietic stem cell transplantation (HSCT) is associated with significant posttransplantation gonadotoxicity. This deficit has been mainly attributed to pretransplantation conditioning, but lower sperm counts in humans also appear to be associated with graft-versus-host disease (GVHD) following allogeneic HSCT. However, the mechanisms leading to diminished spermatocyte levels during GVHD remain unknown. Here we demonstrate that injury to intratesticular cells occurs in unconditioned F 1 mice following the infiltration of donor alloreactive T cells during an acute graft-versus-host reaction (GVHR). Using computer-aided quantitative microscopic morphometry we demonstrate that the nadir of Leydig cell volume density coincides with the peak of intratesticular infiltration by donor T cells. Injury to Leydig cells correlates with an intratesticular inflammatory response characterized by interferon-␥ and tumor necrosis factor-␣ production. These results demonstrate impairment of testosterone-producing Leydig cells during a local alloresponse, thus representing a mechanism that contributes to gonadal insufficiency following allogeneic HSCT. IntroductionHematopoietic stem cell transplantation (HSCT) is the preferred therapy for malignant and nonmalignant disorders. 1,2 To maintain quality of life following HSCT, an appropriate reproductive status is required. A retrospective study conducted by the European Group for Blood and Marrow Transplantation (EBMT) determined, however, that the overall posttransplantation pregnancy rate is currently as low as 0.6%. 3 These results suggested that female HSC transplant recipients become transiently or permanently infertile. Likewise, most male HSC transplant recipients are reversibly or irreversibly infertile due to germ cell injury and/or Leydig cell (LC) insufficiency. [4][5][6] Posttransplantation gonadotoxicity has been attributed to the type and intensity of the pre-HSCT conditioning used. Here, myeloablative and nonmyeloablative reduced-intensity conditioning regimens can induce both spermatocyte injury and impaired LC function. 5,7,8 Gonadal dysfunction has, however, also been associated with the development of graft-versus-host disease (GVHD) because sperm counts in long-term survivors of allogeneic HSCT are much lower in GVHD patients. 9 GVHD remains a major transplantation-related toxicity that is initiated by the recognition of host alloantigens by donor-derived mature T cells, leading to injury in a restricted set of target tissues (ie, skin, liver, gastrointestinal tract). 10,11 The mechanisms leading to diminished spermatocyte levels secondary to GVHD remain unknown. Here we tested the hypothesis that injury to intratesticular cells occurs following the infiltration of alloreactive donor T cells during an acute graft-versus-host reaction (GVHR). Study designMale B6.SJL-Ptprc a Pep3 b /BoyJ mice (B6.CD45.1; H-2 b , CD45.1 ϩ ) were purchased from the Jackson Laboratories (Bar Harbor, ME) and male [C57BL/6 ϫ DBA/2]F 1 (B6D2F 1 , H-2 bd ) mice were obtained from Charl...

alpha-Melanocyte-stimulating hormone (alpha-MSH, alpha-melanotropin) has been shown to be an inhibitory factor in many immunologic and inflammatory processes involving the cytokine interleukin-1 (IL-1). As the mechanism of the interaction between IL-1 and alpha-MSH at the receptor level is unknown, we have studied the role of MC1 melanocortin receptors in two variants of the human melanoma cell line A375 differing in their sensitivity to the cytostatic effects of IL-1 beta. Both IL-1 sensitive (A375r-) and resistant cells (A375r+) carry specific high affinity receptors for IL-1, albeit their concentration is 10-fold higher in A375r+ cells. In A375r- cells, MC1 receptors are absent or below the level for reliable detection in the binding assay. Conversion of A375r- to A375r+ cells by prolonged culture in medium not depleted of endotoxin led to the appearance of MC1 receptors (KD 0.4 +/- 0.123 nmol/l; 608 +/- 134 receptors/cell). Stable transfection of A375r- cells with the human MC1 receptor did not, however, render them resistant to the cytostatic effect of IL-1 beta on concomitant treatment with alpha-MSH or result in the production of IL-6 on treatment with IL-1 beta. Therefore, the presence of MC1 receptors on the surface of A375 cells or their binding to alpha-MSH does not seem to be a factor in cytokine resistance or IL-6 secretion. No interaction between IL-1 beta and alpha-MSH could be demonstrated at the cellular level in this melanoma cell line.

16- and 4-week-old intact and adrenalectomized rats have been treated with different doses of the three glucocorticoids hydrocortisone, prednisolone and dexamethasone by gavage. The delayed feedback effect on plasma ACTH and corticosterone response to an ether stress have been assessed. Almost complete suppression of corticosterone response 20 min after an ether stress and an ACTH suppression to 20% of control values 5 min after an ether stress were observed with 25 µg of dexamethasone, 10 mg of prednisolone and 20 mg of hydrocortisone. Although the percent inhibition of corticosterone and ACTH response to stress was comparable, a striking dissociation of the ACTH and corticosterone release was observed in terms of absolute concentrations. A mean ACTH concentration of 462 ng/l after 25 µg of dexamethasone was measured together with a barely measurable corticosterone concentration of 3 µg%. Similarly, after 10 mg of prednisolone, the mean ACTH concentration was 404 ng/l, whilst the mean corticosterone concentration was 3 µg%. This dissociation demonstrates that the corticosterone concentration on its own does not necessarily reflect the ACTH release. At 4 weeks of age, the ACTH response to stress is more difficult to suppress than in adult animals. This is more obvious after adrenalectomy, where the excessive ACTH secretion was less inhibited by all glucocorticoids used. The time between the last steroid gavage and stress must be considered. In 4-week-old animals the ACTH response 16 h after 12.5 µg of dexamethasone was inhibited by 22%, whereas 4 h after the same dexamethasone dose the inhibition was 85%. It is concluded that under the experimental conditions used, in rats degree and duration of feedback inhibition depend on the total steroid dose applied and on the regimen of drug administration. A dissociation between corticosterone and ACTH release is obvious. A weight-related potency ratio of feedback inhibition was 1:2:400-800 for hydrocortisone to prednisolone to dexamethasone.