Role of cyclic nucleotides in pigment translocation within the freshwater shrimp, Macrobrachium potiuna, erythrophore |
| |
Authors: | L E M Nery M A da Silva A M Lauro Castrucci |
| |
Institution: | Departamento de Fisiologia, Instituto de Biociências, Universidade de S?o Paulo, SP, 05508-900, Brasil e-mail: amdlcast@usp.br, XX
|
| |
Abstract: | The participation of cyclic nucleotide-dependent intracellular signalling pathways in the pigment translocation induced by
pigment-dispersing hormone (α -PDH) or pigment-concentrating hormone (PCH) was investigated in the erythrophores of the freshwater
shrimp, Macrobrachium potiuna. Cholera toxin, forskolin and dibutyryl cyclic adenosine 3′5′ monophosphate (dbcAMP) were able to induce pigment dispersion
with effective agonist concentrations for half maximal response (EC50 s) of 2.8 · 10−11 mol · l−1, 7.0 · 10−7 mol · l−1 and 3.3 · 10−7 mol · l−1, respectively. KT5720 (10−7 mol · l−1 and 10−6 mol · l−1) significantly shifted the dose response curve to α -PDH to the right. Dibutyryl cyclic guanosine 3′5′ monophosphate (dbcGMP)
was ineffective in inducing either pigment aggregation or dispersion. 2′5′ dideoxyadenosine (DDA) and SQ22,536 essentially
elicit a pigment-aggregating response in a dose-dependent manner. These effects were not due to the activation of purinergic
receptors, since concentrations up to 10−4 mol · l−1 of adenosine and adenosine triphosphate (ATP), and up to 10−3 mol · l−1 of uracil triphosphate (UTP) did not elicit pigment aggregation. In order to verify if PCH decreased cyclic adenosine 3′5′
monophosphate (cAMP) levels, cumulative dose-response curves to PCH in the absence and presence of pertussis toxin and 8-MOM-IBMX
were determined. However, neither drug significantly affected PCH activity. The levels of cAMP in the integument cells of
M. potiuna were significantly increased (P < 0.05) by α -PDH (10−7 mol · l−1) and forskolin (10−6 mol · l−1), but were not affected by PCH (10−7 or 10−10 mol · l−1). In conclusion, α -PDH seems to elicit pigment dispersion through the activation of a Gs-protein coupled receptor resulting
in cAMP increase and cAMP-dependent protein kinase (PKA) activation. Furthermore, although a decrease in cAMP was assumed
to be responsible in turn for the action of PCH, such a decrease could not be directly demonstrated.
Accepted: 11 August 1998 |
| |
Keywords: | Pigment-concentrating hormone Pigment-dispersing hormone Cyclic adenosine 3′ 5′ monophosphate Cyclic guanosine 3′ 5′ monophosphate Crustacean erythrophore |
本文献已被 SpringerLink 等数据库收录! |
|