TOWNSEND, K.; SPANINGS-PIERROT, C.; HARTLINE, D.K.; KING, S.; HENRY, R.P.; TOWLE, D.W.: Salinity-Related Changes in Crustacean Hyperglycemic Hormone (CHH) mRNA in Pericardial Organs of the Shore Crab Carcinus maenas

CHH stimulates sodium influx in isolated gills of the crab Pachygrapsus marmoratus, reaching maximum stimulation within 10 minutes (Spanings-Pierrot et al., Gen. Comp. Endocrinol. 119: 340-350, 2000). CHHs from Carcinus maenas sinus gland (SG) and pericardial organ (PO) are identical in the first 40 amino acids but SG-CHH mRNA is spliced, resulting in different C-terminal sequences. The PO-CHH appears not to regulate hemolymph glucose or ecdysteroid synthesis (Dircksen et al., Biochem J. 356: 159-170, 2001). The possibility that PO-CHH might control branchial ion transport was addressed using a molecular approach. We isolated total RNA from pericardial organs and sinus gland/X-organs of male C. maenas acclimated to sea water (35 ppt) or for various times to dilute sea water (10 ppt). Poly-A mRNA was reverse transcribed to cDNA using oligo-dT primer. PCR primers based on published SG- and PO-CHH were employed to amplify the respective targets. In the pericardial organ, we found only the PO-type CHH cDNA sequence. However, in the sinus gland/X-organ, we found both SG-type and PO-type CHH. Estimation of CHH gene expression by quantitative RT-PCR showed that SG-type CHH mRNA changed very little in relation to acclimation salinity. However, expression of PO-type CHH mRNA in the pericardial organ was elevated within two hours after transfer of animals from 35 to 10 ppt salinity, declining to control levels by 24 hours. We suggest that PO-CHH may play a role in stimulating short-term changes in osmoregulatory ion transport across the gills. Supported by NSF IBN-9807539 and the Hancock County Scholars Program.