Histo-cytological responses of the prolactin cells of the catfish Heteropneustes fossilis to cadmium exposure / Respuesta histológica y citológica frente a la exposición a cadmio de las células prolactínicas del pez gato Heteropneustes fossilis

Cadmium is an important metal for modern industrial processes and, being biologically non-essential, poses health hazards to the organisms. In this study we aimed to evaluate the effect of cadmium exposure on the histo-cytology of prolactin cells in the freshwater catfish, Heteropneustes (H.) fossilis. Fish were subjected to 288 mg/L (0.8 of 96 h LC50) and 72 mg/L (0.2 of 96 h LC50) of cadmium chloride for short-term and long-term, respectively. After sacrificing the fish, the blood was collected on 24, 48, 72 and 96 h in short-term and after 7, 14, 21, and 28 days in long-term experiment and analyzed for plasma calcium levels. Also, pituitary glands were fixed on these intervals. The plasma calcium levels of short-term cadmium exposed fish remain unchanged after 24 h. The levels exhibit a progressive decrease from 48 h onwards. The fish exposed to cadmium for 7 days exhibit a decrease in the plasma calcium level. Thereafter, the levels progressively decrease till the end of the experiment (28 days). The prolactin cells of the control fish exhibit structural resemblance to the description given for the prolactin cells of normal H. fossilis. No change in the histological structure and nuclear volume of prolactin cells of cadmium non-exposed fish has been noticed throughout the experiment. In cadmium treated fish, the prolactin cells remain unchanged till 14 days. On day 21, the nuclear volume of these cells exhibits an increase and the cells degranulate. These changes increased profoundly on day 28. In addition, vacuolization and cytolysis were also encountered on day 28 following cadmium treatment. It is concluded that cadmium affects the prolactin cells of the fish H. fossilis thus disturbing the ionic balance.

El cadmio es un metal importante para los procesos industriales modernos, siendo no esencial biológicamente, representa riesgos para la salud de organismos. En este estudio tratamos de evaluar el efecto de la exposición al cadmio por el aspecto histológico y citológico de células secretoras de prolactinas del pez gato de agua dulce Heteropneustes (H.) fossilis. Los peces fueron sometidos a una exposición de 288 mg/L (0,8 de 96 h CL50) and 72 mg/L (0,2 de 96 h CL50) de cloruro de cadmio por a corto y largo término respectivamente. Después del sacrificio de los peces, la sangre fue colectada, tomando muestras de 24, 48, 72 y 96 hs en el corto término y de 7, 14, 21 y 28 días en las sometidas a largo término, la cuales se analizaron para medir niveles de calcio. Además, las glándulas pituitarias fueron fijadas en esos intervalos El nivel plasmático de calcio en los experimentos de exposición a corto tiempo se mantuvo sin cambio tras 24 h. Los niveles exhibieron una caída progresiva a partir de las 48 hs. Los peces expuestos a cadmio por 7 días presentaron una disminución en el nivel plasmático de calcio. Después de esto, los niveles decayeron progresivamente hasta el fin del experimento (28 días). Las células prolactínicas de los peces controles mostraron semejanza estructural a la descripción dada para estas células normales en H. fossilis. No se observaron cambios en la estructura histológica y el volumen nuclear de las células prolactínicas de los peces no expuestos a cadmio a través de todo el experimento. En los peces tratados con cadmio las células prolactínicas se mantuvieron sin cambios hasta los 14 días. En el día 21, el volumen nuclear de esas células se incrementó y estas células presentaron desgranulación. Estos cambios aumentaron profundamente en las muestras del día 28. Adicionalmente en el día 28 posterior al tratamiento con cadmio se encontró vacuolización y citólisis. Se concluyó en que el Cadmo afecta las cñelupas prolactínicas de H fossilis, produciendo disturbios en el balance iónico.

Ultimobranchial gland of freshwater catfish, Heteropneustes fossilis, in response to calcitonin administration

The absence o!!f a hypocalcemic effect of calcitonin (CT) in fishes has been suggested due to exceedingly high plasma levels of CT; the fish may be saturated with respect of circulating CT and therefore unable to respond to exogenously administered CT. Earlier it has been suggested that a hypocalcemic action of injected CT may be obscured by changes in the release of endogenous CT and other calcium regulating hormones. In this study we have used artificial freshwater, calcium-deficient freshwater and calcium-rich freshwater and injected the fish with CT. The aim behind selecting these media were (i) in calcium-deficient medium there would be reduced circulating levels of CT, (ii) in calcium-rich medium there would be diminished secretion of prolactin (this hormone is hypercalcemic in fish), and (iii) by keeping the fish in calcium-rich medium we can test the antihypercalcemic action of CT. Moreover, the present study would reveal the changes in the ultimobranchial gland (UBG) after keeping the fish in all the above three media and/or injecting the fish with CT. Freshwater catfish, Heteropneustes fossilis, were administered intraperitoneally daily with vehicle or 0.5 U/100g body wt of salmon calcitonin (CT) and kept in artificial freshwater, calcium-rich freshwater and calcium-deficient freshwater for 10 days. Blood samples were collected on 1, 3, 5, and 10 days following the treatment and analyzed for serum calcium levels. The ultimobranchial gland (UBG) was also fixed for histological studies on these intervals. In artificial freshwater there was no change in the serum calcium levels of calcitonin-injected fish. The ultimobranchial gland of calcitonin-injected fish exhibited a progressive decrease in the nuclear volume from day 5 onwards. On day 10 vacuolization in the gland was also noticed. In vehicle-injected fish (control) kept in calcium-rich freshwater hypercalcemia has been noticed which persists till the end of the experiment. ...