Occurrence of D-aspartate in the harderian gland of Podarcis s. sicula and its effect on gland secretion.
High concentrations of free D-aspartate (D-Asp), an amino acid well known for its neuroexcitatory activity, are endogeneously present in the Harderian gland (HG) of the lizard Podarcis s. sicula. This orbital gland consists of two different parts: the medial part, which is prevalently a mucous acinar gland, and the lateral part, which is a serous tubulo-acinar gland. To determine the physiological effect of D-Asp on exocrine secretion in HG, D-Asp (2.0 micromol/g b.w.) was injected intraperitoneally into lizards. We found that highest accumulations of exogenous D-Asp in HGs occurred 15 hr after the injection. Specifically, exogenous D-Asp prevalently stimulated serous secretion from the lateral portion of the gland, where immunohistochemical analysis revealed a major accumulation. Similarly, in the medial part of the gland, highly sulfated mucosubstances were observed after D-Asp injection. Further, in both parts of the HG, the electron microscope revealed euchromatic nuclei, a prominent rough endoplasmic reticulum, as well as numerous secretory granules within the acinar cells. Thus, following D-Asp injection, a 60% increase in HG total protein was detected. In addition, exogenous D-Asp induced changes in the electrophoretic pattern of HG. In conclusion, although further investigations are still needed to clarify the molecular pathway induced by D-Asp in exocrine secretion, this study does indicate that free D-Asp plays a significant role in the secretory activity of this gland.
Santillo
A
A
Dipartimento di Scienze della Vita, Seconda Università di Napoli, Caserta, Italy.
Monteforte
R
R
Raucci
F
F
D'Aniello
A
A
Baccari
G Chieffi
GC
D000818:Animals; D026603:D-Aspartic Acid / Q000032:analysis / Q000502:physiology*; D005260:Female; D006243:Harderian Gland / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D007150:Immunohistochemistry; D007274:Injections, Intraperitoneal; D008116:Lizards / Q000502:physiology*; D008297:Male
D026603:D-Aspartic Acid