Assessment of the effect of Fucus vesiculosus extract on the labeling of blood constituents with technetium-99m and the histological modifications on the shape of the red blood cells.

Natural products are widely used as food or food additives or medicines for humans. We are trying to develop a model to assess the possible toxic properties of natural products, such as Fucus vesiculosus, utilized in popular medicine. Red blood cells (RBC) labeled with technetium-99m (99mTc) are used in various procedures in nuclear medicine. This labeling procedure depends on a reducing agent, and stannous chloride is used. There is evidence that this labeling may be altered by drugs. We have investigated the possibility that F. vesiculosus extract is capable of altering the labeling of blood elements with 99mTc. Blood was incubated with F. vesiculosus extract and stannous chloride solution and Tc-99m added. Blood was centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P or BC were also precipitated, centrifuged and insoluble (IF) and soluble (SF) were separated. The percentages of radioativity (%ATI) in BC, IF-P and IF-BC were calculated. Histological preparations of the RBC treated with F. vesiculosus revealed that this extract is capable of promoting important modifications on the shape of the RBC. The%ATI decreased on BC from 93.6+/-2.3 to 29.0+/-2.7, on IF-P from 77.6+/-1.2 to 7.5+/-1.0 and on IF-BC from 80.0+/-3.4 to 12.6+/-4.8. Once the RBC labeling procedure with 99mTc depends on the presence of stannous (+2) ions, the substances present in the F. vesiculosus extract should increase the valence of these ions to stannic (+4). This would decrease the%ATI on blood elements and indicate the presence of oxidant agents in the F. vesiculosus extract.

Gonadotrophin releasing hormone receptors and the response of pituitary gonadotrophs in culture.

We have investigated the effect of the time of culture on cell number, cell content of LH, cell responsiveness to gonadotrophin releasing hormone (GnRH) and binding parameters of GnRH in rat anterior pituitary cells in culture. Although a decrease in the cell number was observed during the culture period, the cell content of LH remained unchanged. The receptor affinity (Ka) in acutely dispersed cells was 0.86 X 10(7) l/mol for [3H]GnRH and 1.36 X 10(10) l/mol for a highly potent agonist, [D-Ser(But)6]GnRH(1-9)nonapeptide-ethylamide (GnRH-A). The affinity and binding capacity (0.3 fmol/10(6) cells) for iodinated GnRH-A did not change significantly during the 6-day culture period. On the contrary, the values of Ka and binding capacity (257 fmol/10(6) cells) for tritiated GnRH decreased by about 50% between days 1 and 6 of culture. Our results suggest that 125I-labelled GnRH-A binds mostly to high-affinity and low-capacity receptor sites, while [3H]GnRH, which must be used at a higher concentration, also binds to low-affinity, high-capacity binding sites and is therefore useless for the measurement of GnRH receptor binding affinity and binding capacity. Since the biological response of the cells to GnRH increased with the time of culture, it is concluded that although GnRH action is receptor-mediated, binding capacity and biological activity are not necessarily correlated.