Cell proliferation kinetic values were established for the epidermis, hair follicle epithelium, and sebaceous glands of 10 Beagles and 4 Cocker Spaniels with healthy skin and coats. Values were established by intradermal pulse-labeling injections of [3H]thymidine, examination of cutaneous biopsied tissues, and autoradiography. The epidermal basal cell-labeling index was 1.41 +/- 0.46% for Beagles and 1.71 +/- 0.56% for Cocker Spaniels. The hair follicle basal cell-labeling index was 1.46 +/- 0.78 and 1.07 +/- 0.42%, respectively. Calculated epidermal cell-renewal time for viable layers of the epidermis was 23.38 +/- 5.93 days for Beagels and 20.97 +/- 4.92 days for Cocker Spaniels. Differences between cell kinetics data for the 2 breeds were not significant (P greater than 0.05). The basal cell-labeling index for the sebaceous gland was significantly (P = 0.009) lower for Cocker Spaniels (0.40 +/- 0.18%) than for Beagles (1.81 +/- 1.08%). Seemingly, epidermal and follicular cell proliferation kinetics in healthy dogs was similar between the 2 breeds, whereas sebaceous gland basal cells were less proliferative in healthy Cocker Spaniels than in healthy Beagles.

Objective: To determine the distribution of cannabinoid receptor type 1 (CB1) and cannabinoid receptor type 2 (CB2) in skin (including hair follicles and sweat and sebaceous glands) of clinically normal dogs and dogs with atopic dermatitis (AD) and to compare results with those for positive control samples for CB1 (hippocampus) and CB2 (lymph nodes). Sample: Skin samples from 5 healthy dogs and 5 dogs with AD and popliteal lymph node and hippocampus samples from 5 cadavers of dogs. Procedures: CB1 and CB2 were immunohistochemically localized in formalin-fixed, paraffin-embedded sections of tissue samples. Results: In skin samples of healthy dogs, CB1 and CB2 immunoreactivity was detected in various types of cells in the epidermis and in cells in the dermis, including perivascular cells with mast cell morphology, fibroblasts, and endothelial cells. In skin samples of dogs with AD, CB1 and CB2 immunoreactivity was stronger than it was in skin samples of healthy dogs. In positive control tissue samples, CB1 immunoreactivity was detected in all areas of the hippocampus, and CB2 immunoreactivity was detected in B-cell zones of lymphoid follicles. Conclusions and Clinical Relevance: The endocannabinoid system and cannabimimetic compounds protect against effects of allergic inflammatory disorders in various species of mammals. Results of the present study contributed to knowledge of the endocannabinoid system and indicated this system may be a target for treatment of immune-mediated and inflammatory disorders such as allergic skin diseases in dogs.

Cell proliferation kinetic values were established for the epidermis, hair follicle epithelium, and sebaceous glands of 8 Cocker Spaniels with primary idiopathic seborrhea. Values were established by intradermal pulse labeling injections of tritiated thymidine followed by cutaneous biopsy and autoradiography.The epidermal basal cell-labeling index was 4.96 +/- 0.97%, and the epidermal nucleated cell-labeling index was 3.33 +/- 0.71%. Calculated epidermal cell renewal time for the viable layers of the epidermis was 7.85 +/- 1.80 days. The hair follicle infundibulum basal cell-labeling index was 5.48 +/- 2.01%, and the sebaceous gland basal cell-labeling index was 5.94 +/- 4.15%. When compared with previously reported cell kinetic values for Cocker Spaniels and Beagles with healthy skin, these data indicate accelerated cellular proliferation in all 3 cutaneous structures in seborrheic Cocker Spaniels.