Stress responsiveness of the pituitary-interrenal axis during early life stages of common carp (Cyprinus carpio)

Abstract

Whole-body levels of ACTH, -MSH and cortisol in eggs and larvae of the common carp (Cyprinus carpio) were determined periodically up until 168 h after fertilisation. ACTH, -MSH and cortisol immunoreactivity was detected in unfertilised eggs, and endogenous production of ACTH and -MSH was observed 24 h after fertilisation and that of cortisol 36 h after fertilisation. ACTH immunoreactivity reached peak levels before hatching (56-72 h after fertilisation) and remained relatively stable thereafter, while -MSH immunoreactivity started to increase after hatching. At 36 h after fertilisation, wholebody cortisol levels increased rapidly reaching peak levels at the end of hatching (72 h after fertilisation), remaining stable until the end of the experiment. From 50 h after fertilisation onwards, embryos and larvae increased their whole-body cortisol levels when subjected to handling (mechanical pressure during egg stage or netting during the larval stage). It is concluded that the pituitaryinterrenal axis in carp is fully functional at the time of hatching. No indications of a stress non-responsive period after hatching were observed.To characterise ACTH and -MSH immunoreactivities in carp larvae, whole-body homogenates were analysed by HPLC, with pituitary homogenates of adult carp serving as a reference. ACTH and -MSH immunoreactivity in carp larvae homogenates consisted of three and two products respectively. HPLC of adult carp pituitaries revealed the presence of two ACTH immunoreactive products, which may represent a phosphorylated and a non-phosphorylated ACTH variant, while the three -MSH peaks most likely represent des-acetylated, mono-acetylated and di-acetylated -MSH, the latter being the predominant form. In carp larvae, however, one of the ACTH immunoreactive products co-eluted with the non-phosphorylated ACTH, while the two -MSH products identified co-eluted with des-acetylated and mono-acetylated -MSH, indicating that POMC processing at this stage of development is different from prohormone processing in adult fish.

Ontogeny of immunoreactive somatolactin, prolactin and growth hormone secretory cells in the developing pituitary gland of Cichlasoma dimerus (Teleostei, Perciformes)

“…In this respect Parhar (1997) showed that secretion of differentiated gonadotrophes during early developmental stages of Oreochromis mossambicus was arrested until GnRH fibers reached the pituitary gland. On the other hand, it was demonstrated that in the common carp Cyprinus carpio ACTH-and MSH-expressing cells were functional before hatching, a few hours after the first ir-cells were identified in the pituitary gland (Stouthart et al 1998). In accordance with these observations it is probable that synthesis and secretion of ADH hormones may be temporally separated in early developmental stages.…”

Immunocytochemical localization and ontogenic development of ?-melanocyte-stimulating hormone (?-MSH) in the brain of a pleuronectiform fish, barfin flounder

“…In the chum salmon, α-MSH cells have been detected in the middle part of the pituitary 2 weeks before hatching (Naito et al 1993). In the common carp, α-MSH-and ACTHexpressing cells are functional before hatching (Stouthart et al 1998). In the ayu, α-MSH-and ACTH-expressing cells have been detected on the day of hatching (Saga et al 1999).…”

Ultrastructure and distribution dynamics of chloride cells in tilapia larvae in fresh water and sea water

“…To exclude effects of handling stress (Stouthart et al 1998), seawater transfer was conducted by changing the water in the aquaria rather than moving the larvae. One day (24 h) after hatching, the osmolarity of one system was gradually but quickly (10 mosmol.min -1 ) increased by addition of artificial sea water, concentrated 3 times, to the water in the plastic aquaria to obtain a salinity of 650 mosmol.kg -1 (20%).…”