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Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation: aquatic / sediment
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented, peer reviewed non-GLP study
Principles of method if other than guideline:
In eels, a CaCl
2
solution was infused into the pneumatic duct vein. Plasma Ca levels were
significantly increased during 3 hr and were followed by significant raises in plasma calcitonin levels. These
results strongly suggest that, in eels, direct raises in blood Ca levels by infusion of a high-Ca solution
via
blood vessels can accelerate the secretion of calcitonin from the ultimobranchial gland.
GLP compliance:
no
Executive summary:

The present results clearly demonstrate that direct raises in blood Ca levels by infusing a high-Ca solution into the blood stream accelerate the secretion of calcitonin from the ultimobranchial gland. In the previous experiment using eels that had been infused a CaCl2solution into the stomach, plasma Ca concentrations were increased from 2.63 mM of the initial value to 6.20 mM at 0.5 hr, 7.45 mM at 1 hr, and 8.50 mM at 3 hr (Suzukiet al., 1999). These values were very similar to the results obtained in this study. On the other hand, in the previous experiment, plasma calcitonin levels were increased from 30 pg/ml of the initial value to 205.6 pg/ml at 0.5 hr, 697.5 pg/ml at 1 hr, and 1118.2 pg/ml at 3 hr. In contrast, the average values in this study were 1,907.8 pg/ml at 0 hr,2,582.1 pg/ml at 0.5 hr, 4,320.7 pg/ml at 1 hr, and 14,005.6 pg/ml at 3 hr. The absolute values of plasma calcitonin were undoubtedly higher in the present experiment. The difference in the values must be due to the differences in the site from which blood samples were taken. In the previous experiment, blood was sampled at the caudal artery; on the other hand, in this study, blood just perfused from the ultimobranchial gland was taken at the arterial bulb. In this study, as mentioned above, the rates of raises in plasma Ca levels were similar to those in the case of the infusion of a high-Ca solution into the stomach (Suzukiet al., 1999). In that experiment, no eels died. Therefore, the raise in plasma Ca levels itself does not seem to be the cause of death of fish. On the other hand, the rate of ionic Ca to total Ca was similar between the high-Ca group and the NaCl group. This fact indicates that ionic Ca infused into the blood stream was immediately combined with some proteins at the same rate as that in the NaCl group. It may be important for a living body to keep the rate of ionic Ca/total Ca constant. However, it is also a fact that the absolute quantity of ionic Ca was very high in the high-Ca group compared to that in the NaCl group. Therefore, an excessive number of Ca ions in the blood stream might result in toxicity. When plasma Ca levels are raisedviathe digestive tract, there may be unknown systems preventing the heart from stopping beating. In our previous experiment, therefore, we should determine the ionic Ca level in plasma. Recently, we knew that, in humans, hypercalcemia harms the function of the heart (Yanget al., 1997; Demerset al., 1998).

Endpoint:
bioaccumulation: aquatic / sediment
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented, peer reviewed non-GLP study
Principles of method if other than guideline:
The effects of vitamin D3, 24,25(OH)2 vitamin D3, 25(OH) vitamin D3 and 1,25(OH)2 vitamin D3 were investigated on the serum calcium and phosphate levels of freshwater catfish, Heteropneustes fossilis. The fish were injected daily intraperitonealy with these secosteroids for 10 days. Blood samples were collected at day 1, 3, 5 and 10. Serum calcium and inorganic phosphate levels were elevated by all of the treatments except for 24,25(OH)2 vitamin D3.
GLP compliance:
no
Executive summary:

The present study concludes that vitamin D3and two of its prime metabolites, 25(OH)D3and 1,25(OH)2D3can affect both calcium and phosphate metabolism in a freshwater te-leost,H. fossilis. We also do not feel it unreasonable to speculate that vitamin D3and 25(OH)D3have to be converted to a more active form, probably 1,25(OH)2D3as these secosteroids produced an effect only on day 3 whereas 1,25(OH)2D3produced an effect in one day. The present results together with those of previous report (Sundell and Bjornsson, 1990) suggest that there exists different functional aspects in the actions of vitamin D3and its metabolites in freshwater teleosts (freshwater environment is hypotonic in relation to the blood where vitamin D3analogs affect calcium homeostasis) and marine teleosts (sea water is hypertonic in relation to the blood where vitamin D3and 1,25(OH)2D3produced contradictory effects;Sundellet al., 1993; Fenwicket al., 1994).

Description of key information

Key value for chemical safety assessment

Additional information

Experimental data on the bioaccumulation potential of tricalcium bis(orthophosphate) are not available. When dissolved in water (and so animal tissues/fluids) the substance will dissociate to the phosphate species and calcium ion, both are essential micronutrients for organisms that are natural ionic components of blood, cell fluids, etc. The uptake and concentration of calcium and phosphate in organisms is controlled and regulated by a number of mechanisms, e.g. excess calcium and phosphate is excreted. In addition, the concentrations of both nutrients are kept on a constant level, which is regulated by hormones like calcitonin (Srivastav et al. 1997, Sasayama et al. 2002). Thus, an accumulation of the both ions in body fats is considered unlikely

Thus, bioaccumulation and secondary poisoning is not anticipated.

References:

Srivastav et al. (1997) Vitamin D metabolites affect serum Calcium and Phosphate in freshwater Catfish, Heteropneustes fossilis. Zoological Science (14), 743-746.

Sasayama et al. (2002) Direct Raises in Blood Ca Levels by Infusing a High-Ca Solution into the Blood Stream Accelerate the Secretion of Calcitonin from the Ultimobranchial Gland in Eels. Zoological Science (19), 1039-1043.