Calcium metabolism and osmoregulation during sexual maturation of river running Atlantic salmon

Abstract

As Atlantic salmon return from the ocean to undertake the anadromous spawning migration up the river of origin, profound changes in calcium metabolism and osmoregulation take place. Using tartrate resistant acid phosphatase as a marker, scale osteoclast activity was found to increase throughout sexual maturation and spawning migration. Thus, the participation of osteoclasts in the elevated scale resorption observed during this phase is established. As calcium was simultaneously accumulated in the female gonads, it is proposed that the scales are resorbed in order to provide calcium for the growing ovaries. Plasma oestradiol-17 levels were elevated in females during sexual maturation, and had decreased at the time of spawning. Plasma testosterone levels were similar in males and females during the first part of the upriver migration, but had increased in males and decreased in females at spawning. In addition to the role of these sex steroids in the gonadal growth, their possible involvement in the increased scale resorption during this phase is discussed. Plasma growth hormone and thyroxine levels were elevated in both sexes at spawning, with the triiodothyronine/thyroxine (T 3 /T 4 ) ratio declining sharply, indicating possible roles for these hormones in the maturational process. The relatively low gill Na + ,K + -ATPase activity of salmon caught in the estuary implies that the fish had already adapted to a hypoosmotic environment. During the upriver migration, the gill Na + ,K + -ATPase activity decreased further, indicating that the hypoosmoregulatory ability was suppressed further during sexual maturation and spawning migration. 1998 The Fisheries Society of the British Isles

Identification of follicular vitellogenesis stage by monitoring of plasma calcium and estradiol-17β concentrations in the cultured Caspian brown trout, Salmo trutta caspius Kessler, 1877

“…The Vtg is released to the circulation and as Vtg binds calcium, total plasma calcium levels increase. Vtg is subsequently sequestered by the oocytes, processed and stored for the nutrition of the embryo (Nagahama 1987;Persson et al 1998). In fact, there is a positive relationship between Vtg concentration and plasma calcium during vitellogenesis stage.…”

Immunohistochemical identification of a vacuolar proton pump (V‐ATPase) in bone‐resorbing cells of an advanced teleost species, Oreochromis niloticus

“…Two enzymes whose activity requires an acid environment have been assigned so far to teleostean osteoclasts: TRAP and -glycerophosphatase (Persson et al, 1995(Persson et al, , 1998Takagi & Kaneko, 1995;Witten, 1997). However, the presence of V-ATPase as a prerequisite for the extracellular activity of these enzymes has not yet been confirmed in bone-resorbing cells of teleosts.…”

“…Recently, multi-and mononucleated bone-resorbing teleost cells have been visualized using histochemical procedures, most notably by demonstration of tartrate-resistant acid phosphatase (TRAP) (Persson et al, 1995(Persson et al, , 1998Takagi & Kaneko, 1995;Witten, 1995Witten, , 1997, which is a well established marker for bone-resorbing cells of mammals (Minkin, 1982;Van De Wijngaert & Burger, 1986). TRAP is widely used for identification of osteoclasts in histological sections, as well as in cell culture and for determination of osteoclast activity (Hermanns, 1987;Jarkowska-Kozlowska & Kozlowski, 1995;Lacey et al, 1998).…”

Swimming performance and blood chemistry in Atlantic salmon spawners exposed to acid river water with elevated aluminium concentrations

“…Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) experienced a larger reduction in critical swimming speed (U-crit) when exposed to acid water with elevated aluminium concentration compared with exposure to acid water alone. Also, sexual maturation affects osmoregulation and calcium homeostasis in salmonids (Persson et al, 1998). Calcium is important in regulating gill permeability thereby preventing loss of plasma ions in freshwater.…”

“…Calcium is important in regulating gill permeability thereby preventing loss of plasma ions in freshwater. Possible changes in gill calcium content combined with a reduced Na + -K + -ATPase activity (Persson et al, 1998) could make sexually mature salmonids more sensitive to acid water compared with immature fish and Atlantic salmon spawners are sensitive to acid water with elevated aluminium levels (Skogheim et al, 1984).…”