D-aspartate modulates transcriptional activity in Harderian gland of frog, Rana esculenta: Morphological and molecular evidence
Article first published online: 2 MAR 2005
Copyright © 2005 Wiley-Liss, Inc.
Journal of Cellular Physiology
Volume 204, Issue 2, pages 445–454, August 2005
How to Cite
Raucci, F., Santillo, A., D'Aniello, A., Chieffi, P. and Baccari, G. C. (2005), D-aspartate modulates transcriptional activity in Harderian gland of frog, Rana esculenta: Morphological and molecular evidence. J. Cell. Physiol., 204: 445–454. doi: 10.1002/jcp.20316
- Issue published online: 26 MAY 2005
- Article first published online: 2 MAR 2005
- Manuscript Accepted: 19 NOV 2004
- Manuscript Received: 22 OCT 2004
- L.R.N.5 (2002). Grant Number: MIUR-COFIN 2002 (prot.2002058717)
In the green frog, Rana esculenta, a substantial amount of D-aspartate (D-Asp) is found endogenously within the Harderian gland (HG) following its synthesis from L-aspartate (L-Asp) by an aspartate racemase. The frog HG is an orbital seromucoid gland that displays seasonal changes in secretory activity. Our in vivo experiments, consisting of i.p. injection of 2.0 μmol/g b.w. D-Asp in frogs collected during two periods of differing glandular activity (high or medium-low secretory activity), revealed that HG can to take up and accumulate D-Asp and that this amino acid may modulate the exocrine secretion through a kinase pathway. At a time when the gland shows relatively low secretory activity, i.p. administration of D-Asp rapidly induced activation of ERK1 and an increase in cells active in RNA synthesis. This increase in transcriptional activity was followed by a significant increase in mucous secretion. By contrast, administration of exogenous D-Asp when HG was showing high activity rapidly induced inhibition of both ERK1 and transcriptional activity. Since D-Asp is known to be recognized by receptors for N-methyl-D-aspartic acid (NMDA), it is possible that in the HG, D-Asp mediated NMDA activation may enhance the kinase pathway. The above activation of opposing stimulatory and inhibitory processes could reflect different levels of NMDA-receptor activity, which could vary as a function of the level of gland activity. This study provides the first evidence of a role for this excitatory amino acid in exocrine secretion. The effects of D-Asp in HG appear to be specific since they were not seen in frogs treated with other D- or L-amino acids with known excitatory effects on neurosecretion. © 2005 Wiley-Liss, Inc.