SUMMARY

The interrenal tissue of the air-breathing fish, Heteropneustes fossilis, became hypertrophied during the breeding period. The interrenal cell cytoplasm became acidophilic and vacuolated, cytoplasmic granulation disappeared and the cell nuclei increased in size. The diameter of the nuclei varied from 2·07 to 3·12 μm in the non-breeding period while in the breeding season there was almost uniform enlargement (4·54 ± 0·36 μm). Variation in nuclear size was most pronounced during maturation of the gonads, i.e. in April. However, the size of larger nuclei (average diameter 6·53 ± 0·98 μm) was not significantly different from that of thesmaller nuclei (average diameter 4·61 ± 0·61 μm) during this period (P > 0·05).

The volume density of the cell components of the interrenal tissue nearly doubled in the breeding period but the relative proportions remained more or less the same. Glycogen granules, which appeared to be uniformly distributed in the interrenal cells in the non-breeding period, became aggregated and clumped in many parts of the cell during the breeding period. There was a clear increase in the chromaffin reaction in the chromaffin cells during the breeding period but the iodate reaction, indicating noradrenaline content, decreased considerably.

In the ovarian cycle there was a close relationship between gonadosomatic index, ova diameter and water temperature. There was a more than tenfold increase in the gonadosomatic index in the breeding period (1·30 in the non-breeding and 15·27 in the breeding periods). In males, the rise in the gonadosomatic index in the breeding period corresponded to that of the ovary in degree (0·22 in the non-breeding and 3·20 in the breeding periods).

In the non-breeding period the thyroid follicles were composed of squamous epithelium (epithelial height 1·2–2·2 μm) with a follicular diameter of 48–76 μm and the colloid completely filling the lumina of the follicles; features indicative of hypofunction of the gland. In the breeding period, the follicles were composed of cuboidal epithelium (epithelial height nearly three times that in the preceding period, 4·1–6·3 μm) follicular diameter was reduced (36–48 μm) and the colloid incompletely filled the lumina, thus suggesting normal or slight hyperfunction of the gland.

ABSTRACT

A previously described in-vitro rat granulosa cell plasminogen activator bioassay for FSH has been modified and applied in the assay of human serum. This modified method consists of exposing the diethylstilboestrol-stimulated granulosa cells from 25- to 26-day-old rats to FSH or test substance for 3·5 h in wells coated with ¹²⁵I-labelled fibrinogen and treated with thrombin. Following stimulation with FSH, the dose-related production of plasminogen activator was measured as the degree of ¹²⁵I-labelled fibrinolysis in the presence of added plasminogen. Using the urinary FSH/LH bioassay reference preparation as the assay standard, the useful range of the assay was 0·3–15IU/l, with an assay sensitivity of 0·3 IU/l. As determined using purified glycoprotein hormone preparations, the assay was highly specific for FSH. The minor degree of FSH bioactivity measured in some of the hormone preparations was accounted for by the amount of FSH contamination in these preparations. To abolish interference caused by unknown serum factors, we heat-treated the serum samples for 15 min at 56 °C before the assay. The results indicated that neither immunoreactivity nor bioactivity was affected by this treatment. Furthermore, heat-treated human sera gave responses parallel to the standard curve at the three dose levels (2, 4 and 8 μl) studied. We used this bioassay to estimate the FSH-like bioactivity in 15 human serum samples. The estimates of immunoreactive FSH in these samples correlated well with the corresponding FSH bioactivity (r = 0·745, n = 15 and P < 0·05).

The results indicate that with this sensitive and rapid (completed within 24 h) bioassay, it should be possible to measure FSH bioactivity in heat-treated human serum samples.

Journal of Endocrinology (1990) 126, 159–168

Rabbit antiserum to human seminal plasma inhibin (hSPI) was administered subcutaneously to developing male rats of 5, 10, 14, 17 and 24 days of age and the size of the endogenous FSH rise in serum was measured. The FSH levels were threefold higher on day 9 and 1·5-fold higher on days 14 and 18 when compared with levels in control rats treated with normal rabbit serum. Furthermore, the in-vitro binding capacity of pituitary plasma membrane to ¹²⁵I-labelled hSPI declined with increase in age of the rats. Thus, the results of the present study suggest that the sensitivity of the testicular inhibin–FSH feedback relationship is related to age-dependent changes in pituitary binding of inhibin.