Confirmation of Luteinizing Hormone (LH) in Living Human Vitreous and the Effect of LH Receptor Reduction on Murine Electroretinogram

Abstract

Luteinizing hormone (LH), produced in the anterior pituitary, has been detected in cadaver eyes and LH receptors (LHRs) have been identified in the retina, with the highest density in cone photoreceptors. Our aim was to confirm the presence of LH in the living, human eye as well as to examine the potential impact of a reduction in LHR signaling on visual processing. Vitreous samples were collected from 40 patients (23 diabetics, 17 non-diabetics) who were undergoing vitrectomies for various indications. LH concentration was quantified in each sample via an electro-chemiluminescence immunoassay and Meso Scale Discovery platform and normalized to total protein. In addition, full-field electroretinography (ERG) was performed on 11 adult LHR knockout heterozygous mice (B6;129X1-Lhcgr^tm1Zmlei/J) and 11 wild types using the Celeris-Diagnosys system. The median LH values (pg/mg total protein) for non-diabetics, diabetics without proliferative diabetic retinopathy (PDR) and diabetics with PDR were 40.7, 41.9 and 167.8 respectively. LH levels were significantly higher in diabetics with PDR. In our ERG investigation, heterozygous LHRKOs were found to have significantly reduced amplitudes of a-wave and b-waves at high stimulus intensities with no significant change in a-wave or b-wave amplitudes at lower intensities; this is consistent with a selective impairment of cone-mediated responses. Our findings confirm LH is present in the adult human eye. Our findings also suggest that a reduction in LH receptor signaling negatively impacts visual processing of the cone photoreceptors. Overall, our study results support the theory that LH likely plays a physiologic role in the eye.

Keywords: ERG; cone cells; electroretinography; luteinizing hormone; photoreceptors; visual processing.

Fig. 1.. Photoresponse deficits in Lhrko^+/−mice.

A) Examples of wild-type and Lhrko^+/− electroretinogram responses to the 465 nm stimulus at 11.8 log (left) and 14.9 log photons cm⁻² s⁻¹ (right). Arrows indicate stimulus timing. B-E) Wild-type vs. Lhrko^+/− comparisons in a-wave latency (panel B), a-wave amplitude (panel C), b-wave latency (panel D) and b-wave amplitude (panel E). In the plots in panels B, C1, D and E1, the first three stimuli are 635 nm red light while the rest are 465 nm blue light. The error bars represent SEM. *, p<0.05. Panels C2 and E2 show box-and-whisker plots for the three light intensities at which significant wild-type vs. Lhrko^+/− differences were found. The lower and upper limits of each box depict the 25^th and 75^th percentiles. The horizontal line and square indicate the median and the mean, respectively. The ends of the whiskers represent the minimum and maximum of the data. The open circles depict all data points.