Cadmium induces changes on ACTH and PRL cells in Podarcis sicula lizard pituitary gland

Abstract

We analyzed the effect of cadmium on corticotropic (ACTH) and prolactin (PRL) cells in the pituitary gland of the Podarcis sicula lizard under chronic exposure to this metal. Adult lizards were given CdCl2 in drinking water at the dose of 10 μg/10 g body mass for 120 days. Light microscopy was performed after histological and immunohistochemical staining, and the effects were followed at regular time intervals up to 120 days post-treatment. We detected substantial variations in the general morphology of the pituitary: unlike the control lizards in which the gland appeared compact, the treated lizards showed a glandular tissue with dilated spaces that were more extensive at 90 and 120 days. PRL and ACTH cells showed an increase in occurrence and immunostaining intensity in treated lizards in comparison with the same cells of control animals. This cellular increase peaked for PRL at 30 days in the rostral, medial and also caudal pars distalis of the gland. ACTH cells appeared to increase markedly after 60 days of treatment in both the pars distalis and the pars intermedia. Again, at 60 days small, isolated ACTH cells were also found in the caudal pars distalis in which these cells were generally absent. However, at 120 days both these cellular types showed an occurrence, distribution and morphology similar to those observed in the control lizards. In lizards, protracted oral exposure to cadmium evidently involves an alteration of the normal morphology of the gland and an inhibitory effect of ACTH and PRL cells, since they increase in occurrence and immunostaining. Yet in time the inhibitory effect of cadmium on ACTH and PRL cells falls back and their occurrence appears similar to that of the control lizard.

Figure 1

Mallory stain. Sagittal sections of the P. sicula pituitary gland. (A) Control lizard showing the extension of the gland. At the top the subdivision of the gland into rostral (RPD), medial (MPD), caudal (CPD) pars distalis and pars intermedia (PI) is reported. (B) Detail of panel A showing the organization of the cellular cordons. (C) Treated lizard at 60 days. The gland tissue shows wide irregular spaces. (D) Detail of panel C: the cellular cordons show a major vascularisation (*), a basal lamina only partly surrounding them (◂) and several cells with altered shape (←). Bar 140 µm in A and C; Bar 40 µm in B and D.

Figure 2

ABC technique. Sagittal sections. (A–F) PRL cells (in brown). (A) Control lizard, showing the occurrence of PRL cells in the RPD and in the MPD. (B, C) Details of panel A showing these isolated cells (B) or organized into small cordons (C). (D) Treated lizard at 30 days, showing the increase in PRL cells extending also into the CPD. (E, F) Details of panel D showing the greater intensity of immunostain of the cytoplasm in the MPD (E) and the CPD (F). (G–L) ACTH cells (in brown). (G) Control lizard, showing the occurrence of ACTH cells in the RPD, the MPD and also in the PI. (H, I) Details of panel G to show their elongated shape and the cytoplasm moderately marked in the RPD (H) and their absence in CPD (I). (J) Treated lizard at 60 days with an evident strong immunostain of ACTH cells, which also appears in the CPD. (K, L) Details of panel J highlighting the marked immunostain of these cells in the RPD (K), as well as their occurrence in the CPD (L). Bar 150 µm in A, D, G, J; Bar 33 µm in B, E, I, L; Bar 15 µm in C, F; Bar 38 µm in H, K.