PP/PYY cells from endocrine pancreas of the scincid lizard Eumeces inexpectatus synthesize ACTH- and alpha-MSH-like molecules

Atrial natriuretic factor: localization in the adrenal gland of the lizard Podarcis sicula and effects on pituitary-adrenal axis activity

The occurrence of atrial natriuretic factor (ANF) immunoreactivity was investigated in the adrenal gland of the lizard Podarcis sicula by avidin-biotinylated peroxidase complex (ABC) immunocytochemical technique: ANF immunoreactivity was present in the chromaffin tissue, and was absent in the steroidogenic tissue. The role of ANF in the modulation of the pituitary-adrenal axis activity was investigated in vivo by intraperitoneal administration of ANF. The effects were evaluated by examination of the morphological and morphometrical features of the tissues, as well as the plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, aldosterone, norepinephrine, and epinephrine. ANF (28 microg/100 g body wt) did not affect ACTH plasma levels, that remained almost unchanged; in contrast, corticosterone plasma levels increased from 6.45 +/- 0.070 ng/ml in carrier-injected lizards to 9.69 +/- 0.080 ng/ml 24 h after the injection; aldosterone levels decreased from 2.19 +/- 0.010 ng/ml in carrier-injected specimens to 0.58 +/- 0.003 ng/ml 24 h after the experimental treatment. In the chromaffin tissue, an increase in the number of epinephrine cells and a decrease in the number of norepinephrine cells were observed, decreasing the numeric norepinephrine/epinephrine cell ratio, from 1.4/1 of control specimens to 0.3/1 24 h after ANF administration. Moreover, norepinephrine plasma levels decreased from 998 +/- 4.600 pg/ml in carrier-injected specimens to 321 +/- 2.230 pg/ml 24 h after ANF administration; epinephrine plasma levels were elevated from 614 +/- 3.410 pg/ml in carrier-injected specimens to 1672 +/- 10.800 pg/ml 24 h after the experimental treatment. The presence of ANF in the adrenal gland suggests that, also in reptiles as in other vertebrates, this peptide, locally released from the chromaffin cells, may modulate the activity of the adrenal gland, probably in a paracrine manner. The effects of ANF on the adrenal gland suggest that this peptide may affect reptilian salt and fluid homeostasis.

ProCRH in the teleost Ameiurus nebulosus: gene cloning and role in LPS-induced stress response

The procorticotrophin-releasing hormone (proCRH) gene from the teleost Ameiurus nebulosus was cloned by direct and inverse PCR-based technologies and characterized. The structure of the proCRH gene shows the presence of four exons and three introns giving a total length of 1416bp. Sequence similarity with the corresponding proCRH coding sequences in Tilapia mossambica and Homo sapiens is 97.7 and 78%, respectively. Western blot experiments performed with an anti-human CRH (1-41) antibody revealed the presence of an immunoreactive molecule with an approximate MW of 18kDa, a value comparable to that of the putative catfish proCRH peptide. These data suggest that proCRH could be active in A. nebulosus without any cleavage. ProCRH immunoreactive molecules were found in the central nervous system (CNS) and were immunocytochemically detected in the head kidney and in the pancreatic gland. Western blot and immunocytochemical experiments showed an increase in proCRH expression in the CNS after 15min but not after 120min exposure to LPS. In contrast, the increased immunopositivity was detectable in the pancreas only after 120min of treatment, but in the head kidney throughout the entire period of exposure. Our findings indicate that the CNS responds to the altered conditions for a shorter period of time than the peripheral organs, suggesting a hierarchical and time-regulated stress response. However, an independent response in the peripheral organs cannot be excluded in this scenario.

Molecular characterization of the leopard gecko POMC gene and expressional change in the testis by acclimation to low temperature and with a short photoperiod

The gene for proopiomelanocortin (POMC), a common precursor of malanotropins, corticotropin, and beta-endorphin, was isolated and analyzed in the squamata species, the leopard gecko, Eublepharis macularius. Leopard gecko POMC (lgPOMC) cDNA is composed of 1299bp, excluding the poly(A) tail, and encodes 270 amino acids. The deduced amino acid sequence showed the same structural organization as that of other species and displayed identity with those of other vertebrates: 68% with mud turtles, 57/57% with African clawed frog A/B, 53% with chickens, and 45% with mice. In a phylogenic tree, the lgPOMC clustered with the sequences of the mud turtle POMC and python POMC. The lgPOMC gene comprises three exons and two introns and this structure is consistent with humans, rats, mice, African clawed frog and zebrafish. RT-PCR analysis revealed that the lgPOMC mRNA was expressed only in the whole brain, pituitary, and gonads. To analyze in more detail, a competitive assay system to quantify the expression levels of POMC mRNA was established. We measured the POMC mRNA expression levels in the leopard gecko testes following transfer from a condition of 29 degrees C, 16L/8D to 18 degrees C, 10L/14D over 6 weeks. This 6-week acclimation increased the POMC mRNA expression levels significantly. This suggests that the leopard gecko POMC-derived peptides play a role in the mediation of the effect of environmental factors on reproduction.

Neuropeptide Y modulates pituitary-adrenal axis activity in the lizard, Podarcis sicula

The role of neuropeptide Y (NPY) in the modulation of the pituitary-adrenal axis activity in a lizard, Podarcis sicula, was investigated by in vivo NPY administration. The effects were evaluated by examination of the morphological and morphometrical features of the tissues as well as the plasma levels of ACTH, corticosterone, aldosterone, norepinephrine, and epinephrine. Intraperitoneally administered NPY (27 nmol /100g body wt) raised ACTH plasma levels (from 5.23+/-0.06 pg/ml in carrier injected specimens to 6.83+/-0.01 pg/ml, 24 h after the injection). In the steroidogenic cells a strong decrease of lipid amount was found; corticosterone plasma level increased from 6.28+/-0.02 ng/ml in carrier injected lizards to 7.96+/-0.01 ng/ml 24 h after the injection); aldosterone levels were raised from 1.88+/-0.02 ng/ml in carrier injected specimens to 6.38+/-0.05 ng/ml 24 h after the experimental treatment. In the chromaffin tissue, an increase in the number of epinephrine cells and a decrease in the number of norepinephrine cells were observed, decreasing the numeric norepinephrine/epinephrine (NE/E) cell ratio, from 1.4/1 of control specimens to 0.5/1 24 h after NPY administration. Moreover, norepinephrine plasma level were elevated from 922+/-4.30 pg/ml in carrier injected specimens to 3075+/-11.30 pg/ml 24 h after NPY administration; epinephrine plasma level increased from 502+/-2.40 pg/ml in carrier injected specimens to 2759+/-8.70 pg/ml 24 h after the experimental treatment. Consistent with these findings, morphological observations showed many chromaffin cells weakly stained and with a reduced content of secretory granules. These results suggest that, in P. sicula, NPY may play a role in the modulation of the pituitary-adrenal axis activity. Previous studies localized NPY in the epinephrine cells of P. sicula adrenal gland; taken together, these results suggest that this peptide might participate in the regulation of adrenal gland activity, enhancing corticosteroid and catecholamine secretion in a paracrine/autocrine manner. The mechanism of action of NPY is discussed.