Fig. S1. Assessment of the orientation of luminescent signal within the pituitary tissue. (A,B) The pituitary was removed from a rat that had received luciferin prior to death. Luminescent signal from the pituitary decreased over time (in the absence of 1 mM luciferin in the surrounding medium). Addition of luciferin after 12 hours caused a large rise in luminescent signal. (C) Cleavage of the distal lobes of a pituitary slice failed to induce a rise in luminescence signal in these newly exposed regions (in the presence of 1 mM luciferin in the surrounding medium). (D) Addition of a further 1 mM luciferin into the surrounding medium following 60 hours of sequential imaging failed to elicit a rise in prolactin transcription. Numbers in A and C indicate the time in hours.

Fig. S2. The effect of different treatments on the expression of prolactin in luminescent pituitary tissue slices over time. Pituitary slices were imaged with luminescent microscopy and stimulated with 1 M dopamine, 5 M forskolin and 0.5 M BayK8644 (FBK) or left unstimulated. Luminescent intensity values were compared at 6 hours, 24 hours and 48 hours (represented as fold change over initial values). Graph shows mean and standard deviation (bars) for (A) three male pituitary slices in each condition, and (B) one female pituitary slice in each condition.

Fig. S3. Comparison of luminescent intensity between different male transgenic rat lines. The intensity of the whole pituitary and dispersed pituitary cells was measured using luminescent microscopy in unstimulated conditions. Graph shows mean and standard deviation (bars) for two pituitaries and at least 20 cells of each transgenic line; low copy number line 37A and high copy line 49.